Study Guide For Me
All of the following are true of installing the distributor EXCEPT:
On a 4-cylinder engine, the distributor can be timed just after TDC on cylinder #4.: Regardless of the number of cylinders, the distributor should be timed to cylinder #1.
A multi-trace oscilloscope can test all of the following EXCEPT:
Air/fuel ratio: The air/fuel ratio cannot be tested using an oscilloscope. A 4- or 5-gas analyzer would be used for this task.
A hesitation during acceleration from a stop on a fuel-injected engine may be caused by all of the following EXCEPT:
A faulty speed sensor will affect the electronic engine control system, but not in a way that would cause a hesitation.
Technician A says a single-cylinder misfire diagnostic trouble code can be caused by a defective coil on some vehicles. Technician B says a low fuel-pump pressure can cause a single-cylinder misfire diagnostic trouble code. Who is correct?
A only
If the vacuum drops slowly to a low reading when a vacuum gauge is connected to the intake manifold and the engine is accelerated and held at a steady speed, then which of the following is the most likely cause?
A restricted exhaust can be diagnosed using a vacuum gauge. With the gauge connected to the intake manifold, increase the RPM to 2.000 rpm and observe the gauge. If the vacuum slowly drops as the RPM is held at 2.000 rpm. then the exhaust could be restricted.
A technician is performing a compression test. Which statement below is most likely true?
All cylinders reading even, but lower than normal, may be caused by a slipped timing chain.: A slipped timing chain will usually show low and even compression on all the cylinders.
All of the following can cause the engine to spark knock EXCEPT:
A stuck-open exhaust gas recirculation (EGR) valve: The EGR system is used to control combustion chamber temperature, by redirecting inert exhaust gas by into the cylinder. An EGR valve stuck open would cause a rough idle or maybe a stall out at idle, but it would not cause spark knock.
An SFI vehicle stalls intermittently at idle and has negative long-term fuel trim correction values stored when checked with a scan tool. All of the following conditions could cause this EXCEPT:
A vacuum leak: A vacuum leak would cause a high idle and fuel trim to go positive not negative.
All of the following are true of the cylinder leakage test EXCEPT:
Air loss and bubbles in the radiator indicate a bad intake valve guide: When performing a cylinder leakage test, air is injected into the cylinder with the piston at TDC on the compression stroke. Air loss or bubbles in the radiator indicate a bad head gasket or cracked head or block.
All of the following statements about powertrain control module (PCM) inputs are true EXCEPT:
An analog meter may be used for diagnosis.: Most analog meters are low impedance, meaning they have low internal resistance. These types of meters can draw more amperage than a circuit can handle, so they are not used when testing computer circuits.
All of the following could cause high starter current readings EXCEPT:
An open circuit: An open circuit would not allow any current flow.
All of the following are part of the secondary air system EXCEPT:
Back pressure transducer: The back pressure transducer is part of the exhaust gas recirculation system.
Technician A says a damaged or missing air filter can increase wear on cylinder walls. Technician B says an air filter problem can affect fuel consumption. Who is correct?
Both Technicians are correct. A damaged or missing air filter will allow dirt particles to enter the combustion chamber and cause abrasive wear to the cylinder walls. If the air filter gets dirty, then it becomes harder and harder for the air to enter the intake manifold. This causes the air/fuel mixture to become rich, causing excessive fuel consumption and drivability complaints.
Technician A says a fuel-pressure test is performed to test fuel pump operation. Technician B says it is possible to have a good fuel pressure reading and insufficient fuel flow. Who is correct?
Both Technicians are correct. A fuel pressure test is performed to test the ability of the fuel pump to produce the correct pressure needed to operate the vehicle. A fuel pump can have good pressure and still not have enough flow or volume. A restricted fuel filter is usually the cause of this problem.
Technician A says a greenish corrosion on terminals results in high resistance in the circuit. Technician B says loose retaining lock tabs on a terminal can cause high resistance in connector terminals. Who is correct?
Both Technicians are correct. A greenish corrosion known as green death results from moisture at a terminal. If left unattended long enough, the terminal will be completely corroded away. This causes a high resistance in the circuit. Another common cause of high resistance in a wiring circuit is a broken terminal lock tab, which could cause the terminal to push out of the connector and become disconnected.
Technician A says oil found inside the air filter housing may be caused by excessive crankcase blow-by. Technician B says a plugged PCV valve will cause excessive crankcase pressure. Who is correct?
Both Technicians are correct. A positive crankcase ventilation system vents the engine from excessive crankcase pressures. Excessive crankcase pressure can cause oil in the air cleaner, leaking seals, and leaking gaskets. If any of these conditions are present, then the PCV system should be inspected and tested.
Technician A says a pressure drop test can be performed to test for a restricted fuel filter. Technician B says some vehicles do not use an in-line filter; the fuel filter is in the fuel tank. Who is correct?
Both Technicians are correct. A pressure drop test is a very accurate way to check for a restricted fuel filter; however, some vehicles do not have a fuel filter inline to the fuel injector. Their fuel filter is in the fuel tank and is part of the fuel pump module.
A mass air flow (MAF) load-calculating-type port fuel-injected engine runs fine at idle, but hesitates under acceleration. No DTCs are stored. Technician A says to check for a restricted MAF inlet screen. Technician B says a bad spot in the throttle position sensor signal could be the cause. Who is correct?
Both Technicians are correct. A restricted MAF inlet screen will cause an improper response from the sensor and a hesitation under acceleration. A TPS signal that drops out will cause the computer to reduce fuel flow thinking the throttle was closing, causing a hesitation under acceleration.
Technician A says restricted exhaust may cause reduced fuel economy. Technician B says restricted exhaust causes reduced engine efficiency. Who is correct?
Both Technicians are correct. A restricted exhaust prevents the engine from drawing in the needed air/fuel mixture because it cannot get rid of the inert exhaust fast enough. Restricted exhaust lowers power, fuel economy, and engine efficiency.
Technician A says to use a scan tool to verify throttle position sensor input and related diagnostic trouble codes (DTCs). Technician B says coolant-temperature sensor input is used to help determine open- and closed-loop status. Who is correct?
Both Technicians are correct. A scan tool can be used to monitor TPS (throttle position sensor) readings in voltage as well as degree of opening. If an open or short occurs in the TPS circuit, then a DTC will be stored in the PCM. The coolant-temperature sensor is one of the inputs that determine when the engine enters closed-loop status.
Technician A says a stethoscope can be used to pinpoint engine noises. Technician B says you may use a long screwdriver for noise diagnosis if a stethoscope is not available. Who is correct?
Both Technicians are correct. A stethoscope is a good tool to use to help diagnose an engine noise: if a stethoscope is not available, then a long screwdriver can be used to listen to noises.
Technician A says the exhaust can be checked for restrictions using a vacuum gauge. Technician B says the back pressure in the exhaust should not exceed 1.5 pounds per square inch (PSI) at idle. Who is correct?
Both Technicians are correct. A vacuum gauge is used to test for exhaust restriction. A vehicle with restricted exhaust will have a low vacuum reading at 2,000 rpm and possibly slowly drop even lower as the RPM is held. The best method for checking the exhaust for restriction is to check exhaust back pressure, which should not exceed 1.5 psi at idle and 2.5 psi at 2,000 rpm.
Technician A says a vehicle with a restricted fuel filter can still have fuel pressure within the specifications. Technician B says if a restricted fuel filter is suspected, then a fuel pump volume test can be performed. Who is correct?
Both Technicians are correct. While a restricted fuel filter will affect the amount (volume) of fuel that can be pumped, it will not affect pressure.
Technician A says a vacuum leak can occur under the intake manifold and cause oil consumption. Technician B says propane is a good method for locating vacuum leaks. Who is correct?
Both Technicians are correct. A vacuum leak under the intake manifold can be hard to diagnose. A good indication of a vacuum leak under the intake manifold is the complaint of excessive oil consumption coupled with a drivability complaint. A can of propane connected by an adapter to a long hose can help to access hard-to-reach places. When checking for vacuum leaks, note that the engine RPM will rise or falldepending on the air/fuel mixture at the time the leak is found.
Technician A says the alternator connectors should always be inspected for corrosion and/or distortion from overheating when replacing an alternator. Technician B says some replacement alternators come with a new connector. Who is correct?
Both Technicians are correct. Alternator connectors should always be inspected for corrosion and/or distortion from overheating. Some replacement alternators come with a new connector.
A vehicle is being diagnosed for a poor drivability complaint. The vehicle also fails to start at times; it just cranks with no start. Technician A says the charging system could be undercharging at times. Technician B says an under- or overcharging system should generate a trouble code. Who is correct?
Both Technicians are correct. An undercharged system would not keep the battery at a full state of charge, but should generate a diagnostic trouble code for over or undercharging.
Technician A says when high voltage drop is found in a circuit, check for burned wires, connector ring terminals, loose retaining nuts, or other wire and connector concerns. Technician B says that greenish white corrosion can happen at any point where the wire insulation has been pierced or opened in any way. Who is correct?
Both Technicians are correct. Anything that increases the resistance in a circuit will increase the voltage drop in a circuit. When voltage drop is found, check for loose connections and loose splices. Also look for signs of greenish white corrosion.
Technician A says that worn valve train components usually produce a clicking noise. Technician B says an engine noise diagnosis should be performed before doing engine repair work. Who is correct?
Both Technicians are correct. Before any engine repair work is performed, the cause of the noise must he identified. A clicking noise is usually in the valve train. A double-knocking noise is usually a piston wrist pin. A low-sounding knock heard on startup is usually a main bearing. A rod hearing produces a knock on acceleration.
During a cylinder leak down test on a 6-cylinder engine, air is heard coming from the #2 spark plug hole as cylinder #3 is being checked. Technician A says that this could be caused by a blown head gasket. Technician B says this could be caused by a cracked engine block. Who is correct?
Both Technicians are correct. During a leak down test, air is injected into the cylinder while the piston is at TDC of the compression stroke. If air is heard escaping from an adjacent cylinder, a blown head gasket or cracked head or block should be suspected.
Technician A says a secondary air-injection system directs output from the air pump to the exhaust manifold during engine warm-up and switches air to the catalytic converter during closed-loop operation. Technician B says air injection will have little or no effect on tailpipe carbon dioxide readings. Who is correct?
Both Technicians are correct. During warm-up, the secondary air is directed upstream to the exhaust manifold. After the vehicle enters closed-loop mode, the secondary air is directed downstream to the catalytic converter. A carbon dioxide reading indicates engine efficiency and is riot affected by the secondary air pump.
Technician A says that enabling criteria are specific conditions that must be met before a monitor will run, such as coolant temperature or engine speed. Technician B says that pending conditions are conditions that exist that prevent a specific monitor from running, such as an oxygen sensor fault code preventing an oxygen sensor heater monitor from running. Who is correct?
Both Technicians are correct. Enabling criteria are the specific operating parameters that must be met before a monitor will run. Many EVAP monitors, for instance, require a cold start with ambient temperature below a certain value. Pending conditions are any circumstances that may prevent a monitor from running properly, such as an oxygen sensor fault not allowing a catalyst monitor to run.
Technician A says that a 12-volt test light connected between the negative side of an ignition coil and ground that blinks on and off during cranking confirms the primary circuit is being switched. Technician B says any voltage drops greater than .3 volts in the primary circuit can reduce secondary circuit kV output. Who is correct?
Both Technicians are correct. If the test light blinks when the engine is cranked, it verifies the primary circuit is being switched to ground and then off. Any voltage drop in the primary circuit will affect the amount of secondary voltage produced. A 1-volt voltage drop in the primary can lower the secondary voltage by as much as 10,000 volts.
Technician A says a manifold absolute pressure (MAP) sensor should be able to hold vacuum during a test. Technician B says some MAP sensors produce an analog voltage signal while others produce a digital square wave signal. Who is correct?
Both Technicians are correct. MAP sensors can be analog or digital. Analog typically produces a direct-current voltage signal while digital sensors produce a frequency. Either type should be able to hold a vacuum without leak down.
Technician A says charcoal canister filters are no longer serviceable. Technician B says gas caps with pressure and vacuum valves must be checked for leakage with a pressure tester. Who is correct?
Both Technicians are correct. Many years ago, the charcoal canister had a fiber-type filter that was replaced during a tune-up, but new late-model vehicles no longer have a filter that is serviceable. Canisters today are sealed units. With the enhanced EVM system, the need for gas caps that seal well is crucial. When diagnosing an EVAP leak code, a special pressure tester is used to test the sealing action of the gas cap.
Technician A says that when vacuum is applied to some exhaust gas recirculation (EGR) valves with the engine idling, the EGR valve should open and idle should become erratic. Technician B says that some EGR valves can be opened with a scan tool. Who is correct?
Both Technicians are correct. Most diaphragm-type EGR valves can be tested for proper movement by applying vacuum to the valve at idle and watching for a drop in engine idle. A scan tool also can be used to open the EGR valve for testing purposes if the vehicle is equipped with electronic EGR valves.
Technician A says that nylon fuel line should be routed in a way to prevent kinking. Technician B says nylon fuel line can be repaired on some vehicles; if not, the entire line must be replaced. Who is correct?
Both Technicians are correct. Most late-model vehicles use nylon fuel line. When replacing nylon fuel line, care must be taken not to cause a kink, which restricts fuel flow. Sometimes the nylon fuel line is repairable. Repair can only be made with a special nylon fuel line repair kit.
Refer to the above illustration. Technician A says the check salves allow air in the exhaust without exhaust getting in the air diverter valve. Technician B says the air bypass valve prevents secondary air from entering the exhaust on deceleration. Who is correct?
Both Technicians are correct. On a cold engine the secondary air is diverted upstream in the exhaust manifold. Once the engine enters closed loop, the secondary air is diverted downstream to the catalytic converters. On deceleration, the secondary air is bypassed to the atmosphere through the bypass valve. The check valves prevent the exhaust from entering the diverter valve, which would be damaged by the hot exhaust.
Technician A says when replacing the powertrain control module (PCM), the new PCM may have to be reprogrammed in order for it to operate. Technician B says some drivability problems can be fixed by reprogramming the PCM. Who is correct?
Both Technicians are correct. On many vehicles, the PCM must be reprogrammed when it is replaced. Sometimes a reprogramming (re-flashing) is necessary to correct drivability complaints.
Technician A says when testing an ignition related no-start problem, the technician should always check for available spark at an ignition wire first. Technician B says if a test light is connected to the negative side of the coil while cranking and the test light flickers, then the secondary ignition system needs to be tested. Who is correct?
Both Technicians are correct. One of the first steps in diagnosing a no-start is to check for spark at one of the secondary ignition wires. With a test light connected between the negative terminal of the ignition coil and ground, crank the engine and watch for a flashing test light. This indicates the primary ignition system is switching correctly, so the secondary should be checked.
A vehicle with a MIL illuminated is being diagnosed. The DTC stored in the PCM is P0300 (Random/Multiple-Cylinder Misfire Detected). Technician A says this is a one-trip failure, because catalyst damage can occur. Technician B says the MIL will flash on this type of code. Who is correct?
Both Technicians are correct. PO3XX codes are ignition system or misfire codes A cylinder miss can damage the catalytic converter. If a cylinder miss isdetected, the MIL will begin flashing to alert the driver.
Technician A says a faulty cam shaft position sensor can cause a no-start condition. Technician B says some vehicles will start without an operating camshaft position sensor (CMP). Who is correct?
Both Technicians are correct. The CMP is used in conjunction with the crankshaft position sensor (CKP) to detect which cylinder is firing for spark and as a reference to time the sequential fuel injection. Most vehicles will not start without the CMP signal; however, some vehicles will.
Technician A says that an EGR valve stuck closed will cause detonation. Technician B says that an EGR valve stuck closed will cause high NOx emissions. Who is correct?
Both Technicians are correct. The EGR valve is used to lower the formation of NOx. It does this by redirecting a controlled amount of exhaust gas to the intake manifold. The exhaust gas is inert, meaning it can't be re-burned, so the inert gas takes up space in the combustion chamber that would otherwise have fuel and air in it. This lowers the combustion chamber temperature, reducing the formation of NOx and the possibility of detonation.
Technician A says a defective MAP sensor may cause a lean air/fuel ratio. Technician B says the MAP sensor can cause a no start. Who is correct?
Both Technicians are correct. The MAP sensor measures engine load on a speed density system and relays this information to the PCM for injector pulse width and fuel trim corrections. On some occasions, the MAP sensor can cause a no-start.
Technician A says to use an anti-backfire valve to prevent backfiring during deceleration on pump-driven air-injection systems. Technician B says to prevent exhaust gases from back- flowing into the air-injection control valves or pump, check valves can be used in the exhaust manifold and converter feed pipes. Who is correct?
Both Technicians are correct. The anti-backfire valve, sometimes called the diverter valve, helps prevent a backfire in the exhaust on deceleration. To protect the secondary injection system from hot exhaust, check valves are used. These valves allow air in from the air pump but no exhaust out to the secondary air-injection components.
Technician A says DTC should be erased using a scan tool. Technician B says the monitor for the related fault should be run before the vehicle is returned to the customer. Who is correct?
Both Technicians are correct. The best method for erasing diagnostic trouble codes is to use a scan tool. Before the vehicle is returned to the customer, however. the monitor for the fault that was repaired should be run to verify the repair.
While scanning an OBD II vehicle for DTCs, a P1000 is retrieved. Technician A says that a first digit of P means the code is a powertrain trouble code. Technician B says that a second digit of 1 means the code is a manufacturer-specific code. Who is correct?
Both Technicians are correct. The first digit of a code indicates what type of code it is (P for powertrain, B for body, U for network, and C for chassis). The second digit indicates whether the code is generic or manufacturer-specific (1 for manufacturer-specific and 0 for generic).
A scan test of the computer system on a late-model fuel-injected engine reveals a bank #1 long- term fuel trim value of-19, and a bank #2 long-term fuel trim value of-18 with the engine idling. Technician A says these readings could be caused by a defective fuel pressure regulator. Technician B says a restricted fuel return line could cause these readings. Who is correct?
Both Technicians are correct. The fuel trim readings show that the PCM is subtracting fuel, so it is leaning down the air/fuel mixture. A defective fuel pressure regulator can cause these types of fuel trim readings if it sticks and causes high fuel pressure. A restricted fuel return line will cause high fuel pressures, resulting in a negative fuel trim.
Technician A says the electrolyte level is important in a non-serviceable battery. Technician B says on some batteries, the electrolyte level can be checked in a sealed battery by looking through the translucent battery case. Who is correct?
Both Technicians are correct. The level of the electrolytes is critical in any battery regardless of its serviceability. On some batteries, the case is translucent (clear) with the full line clearly marked, giving the technician the ability to quickly check the electrolyte level.
A vehicle has a low power complaint with a hissing sound coming from under the vehicle at wide-open throttle (WOT). Technician A says the exhaust back pressure should be checked. Technician B says the manifold vacuum should be checked. Who is correct?
Both Technicians are correct. The low power with a hissing noise is a good indication of a restricted exhaust. A back-pressure gauge or a vacuum gauge can be used to check for a restricted exhaust. If the back pressure exceeds 2.5 psi at 2,500 rpm or the vacuum drops and continues to drop at 2,500 rpm, then a restricted exhaust is indicated.
Technician A says that if an emissions-related diagnostic trouble code (DTC) is set, then a freeze frame is also stored. Technician B says if an emissions-related DTC is set, then the malfunction indicator lamp will illuminate. Who is correct?
Both Technicians are correct. The malfunction indicator lamp illuminates to warn the driver that the vehicle is malfunctioning and emitting emissions 1.5 times the federal test procedure allowance. When an emissions-related fault is set, a freeze frame of the scan tool data is stored in the PCM.
Technician A says a leaking gas cap gasket can cause an evaporative emissions failure. Technician B says some evaporative emissions canisters have a replaceable filter. Who is correct?
Both Technicians are correct. The purpose of the evaporative emissions system is to prevent the release of gasoline vapors into the atmosphere. A leaking gas cap will cause the malfunctioning indicator lamp to illuminate on a vehicle with enhanced EVAP system. On older vehicles the vapor canisters use a fiberglass-type canister filter that is replaced during maintenance service intervals.
Technician A says that when checking a pulsed-air secondary air-injection system, exhaust pressure pulses felt at the fresh-air intake hose indicate a bad check or reed valve. Technician B says that when testing secondary air-injection systems, the gas analyzer can be used to confirm normal air-injection operation. Who is correct?
Both Technicians are correct. The secondary air system is used to supply additional air to the catalytic converter. Some systems use an air pump. Some use only check valves or reed valves, and some use both. Any exhaust felt at the check valve is an indication of a bad check valve. The gas analyzer can be used to verify secondary air-injection operation.
Technician A says some manufacturers do not allow the cleaning of a throttle body with throttle body cleaner. Technician B says a buildup of gum and carbon deposits may cause rough idle operation. Who is correct?
Both Technicians are correct. The throttle body will begin to have a buildup of carbon over time on some throttle bodies. This causes the idle air control valve to open more to compensate. If the carbon buildup is had enough, then a rough idle or stalling can occur. Some manufacturers to not allow the cleaning of throttle bodies—they require the replacement of the throttle body if it has carbon buildup.
Technician A says most 2-wire COP systems use individual ignition control modules for each cylinder. Technician B says a 4-wire COP coil is checked like any other ignition coil. Who is correct?
Both Technicians are correct. There are basically two different types of COP systems. A 4-wire COP has the ignition module integrated with the coil. A 2-wire COP has a remote ignition control module. The coil on both types is tested like any other coil.
Technician A says one of the first steps in diagnosing a drivability complaint is to verify the driver's complaint. Technician B says one of the first steps in diagnosing a drivability complaint is to perform a thorough visual inspection. Who is correct?
Both Technicians are correct. When diagnosing drivability complaints, the first step is to verify the customer's complaint. Sometimes problems can be fixed by simply performing a good visual inspection. Problems like cracked vacuum hoses, wiring problems, and leaks often can be found with a visual check.
The result of a battery load test done at 78◦F with a carbon pile load tester is 8.9 volts. Technician A says minimum load test voltage is 9.6 volts, and this result is unacceptable. Technician B says that you should compare the results to the tables from the tool or battery manufacturer for temperature correction. Who is correct?
Both Technicians are correct. When load testing the battery, half of the battery's rated cold cranking amps is applied to the battery for 15 seconds. For temperatures above 70°F, the voltage should not fall below 9.6 volts. If the battery is being tested at temperatures below 70°F, then a temperature correction chart must be used.
Technician A says to repeat the pressure test after repairs are made to the cooling system to ensure that all leaks are found. Technician B says a cooling system pressure test should include testing the radiator cap. Who is correct?
Both Technicians are correct. When repairing a cooling system leak, the system should be rechecked after the repair is made to ensure that no other problems exist. The radiator cap should be included in the cooling system pressure test.
Technician A says an ignition coil should be tested for both primary and secondary winding resistance. Technician B says available coil output can be tested with an oscilloscope. Who is correct?
Both Technicians are correct. When testing an ignition coil, the primary and secondary resistance should be measured. The available voltage or maximum voltage can be checked using an oscilloscope.
Technician A says when testing the ignition coil, both the primary and secondary winding should be checked for resistance. Technician B says maximum coil output testing can be performed with an oscilloscope. Who is correct
Both Technicians are correct. When testing the ignition coil, the coil resistance of the primary and secondary windings should be compared with the manufacturer's specifications. The primary winding should measure low, around 1 to 2 ohms. The secondary winding should measure around 8,000 to 12,000 ohms. Another test that can be performed is a maximum coil output test; this can be performed using an oscilloscope.
A primary ignition circuit on a vehicle checks good, but there is no spark from the spark plug wire. There is spark at the coil wire. This could be caused by any of the following:
Broken distributor gear: A broken distributor gear would not allow any spark.
Which of the following is not a cause of a noisy valve train?
High oil pressure: High oil pressure would not cause noise; however, low oil pressure can cause valve train noise.
A vehicle has a DTC for an open vehicle speed sensor circuit. Which of the following systems would most likely be affected?
Cruise control system: The cruise control system uses the vehicle-speed sensor (VSS) for MPH input. Usually if a vehicle has a VSS DTC, then the cruise control also does not operate.
Which of the following is the LEAST LIKELY cause of poor fuel mileage on a vehicle with sequential fuel injection (SFI)?
Defective speed sensor: A defective speed sensor would affect the speed control and speedometer, but would not affect fuel mileage.
Nylon fuel lines should be inspected for all of the following EXCEPT:
Discoloration: Nylon lines can become discolored over time. This discoloration does not affect the integrity of the line.
Which of the following is the most likely symptom resulting from an evaporative emissions system failure?
Fuel odor: The release of fuel vapors would produce a fuel odor.
A cylinder misfire will cause all the following EXCEPT:
High carbon dioxide readings: CO2 readings are engine efficiency indicators. A missing engine would have a low CO2 reading.
All of the following are true when testing a pickup coil EXCEPT:
If adjustable, then the gap should be checked with a steel feeler gauge.: Some pickup coils are adjustable and should be adjusted using a brass feeler gauge. The magnet in the pickup coil will simulate a drag against the steel feeler gauge, giving a false reading.
The PCM sends a digital signal to the ignition control module to control which of the following?
Ignition timing: After the engine starts, the PCM takes control of the timing by sending a digital signal to the ignition module.
All of the following could cause an EVAP system large leak code to be set EXCEPT:
Leaking injector 0-ring: The injector is not part of the EVAP system. A leaking o-ring would cause a drivability problem, but would not set a large leak code.
Low battery or system voltage can cause all of the following EXCEPT:
Low battery voltage will not cause the steering effort to increase.
A vehicle with sequential fuel injection (SFI) has high fuel-pump pressure at idle. Which of the following could be the cause?
Low manifold vacuum: Manifold vacuum is used by the fuel regulator to control fuel pressure; as the manifold vacuum drops, the fuel pressure increases. With the vacuum hose removed from the fuel regulator, the fuel pressure should increase about 10 psi.
Which of the follow diagnostic trouble codes are the highest priority codes and should be diagnosed first?
Misfire-related trouble codes: When a misfire occurs, the catalytic converter can be damaged; thus, misfire codes are of the highest priori and should be diagnosed first.
What behavior should a viscous-drive fan clutch exhibit when rotated by hand with the engine off?
More resistance hot: A hot engine requires a lot of air flow through the radiator for cooling, especially at idle. The hotter the engine, the more the resistance will get in the viscous-drive fan clutch.
An engine has a lack of power and excessive fuel consumption. Technician A says a broken timing belt could be the cause. Technician B says the timing belt may have jumped a tooth 180 degrees out of time. Who is correct?
Neither Technician is correct. A timing belt that was one tooth off could cause this complaint; however, a broken or jumped timing belt 180 degrees would cause a no-start.
Technician A says fuel pressure readings that are above specifications could be caused by a stuck-open fuel pressure regulator. Technician B says if fuel is present at the vacuum hose port of a fuel pressure regulator, then the regulator is stuck open. Who is correct?
Neither Technician is correct. Fuel pressure higher than specifications can be caused by a stuck-closed fuel pressure regulator or a restriction in the return line on a return-type fuel system.
Technician A says the EGR system is used to raise combustion chamber temperature. Technician B says that EGR systems that use an EGR valve position sensor should read about .7 volts with the EGR valve at full open. Who is correct?
Neither Technician is correct. The EGR system is used to lower combustion chamber temperature in order to limit NOx formation in the engine. Some manufacturers use an EGR position sensor for feedback of EGR pintle position.
A vehicle is being diagnosed for a P0134 DTC (Oxygen Sensor Circuit, No Activity Detected) (bank #1, sensor #1). Technician A says the problem could be high fuel system pressure. Technician B says the problem is more likely confined to the downstream oxygen sensor on the bank containing cylinder #1. Who is correct?
Neither Technician is correct. The oxygen sensors typically are labeled as HO2S 1/1 (bank #1, sensor #1), HO2S 1/2 (bank #1, sensor #2), HO2S 2/1 (bank #2, sensor #1). Bank #1 is located on the same side as cylinder #1. Sensor #1 is the upstream and sensor #2 is the downstream.
Technician A says the wastegate on a turbo charger closes to control boost by redirecting exhaust gasses around the turbine. Technician B says once boost pressure is under control, the wastegate opens completely. Who is correct?
Neither Technician is correct. The wastegate is used to control the boost of a turbocharger. If the boost pressure exceeds the wastegate diaphragm rating, then the wastegate will open to lower the boost. Once the boost is under control, the wastegate will close.
While performing a valve adjustment, Technician A says the crankshaft must be placed in position so the piston is at top dead center (TDC) on the exhaust stroke. Technician B says that adjusting valves with too much clearance may cause rough running and burnt valves. Who is correct?
Neither Technician is correct. When adjusting valve, some manufacturers specify on a cold engine and some on a hot engine. The piston must be at TDC on the compression stroke.
An EGR vacuum regulator solenoid (EGRV) is thought to be inoperative. Technician A says when measuring the resistance of the solenoid, a lower-than-specified reading means the windings are open. Technician B says an infinite reading means the winding is shorted. Who is correct?
Neither Technician is correct. When diagnosing a solenoid, the solenoid is measured for resistance and compared to the specification. If the solenoid resistance is lower or higher than the specification, then replace the solenoid.
Technician A says the PCV valve flow is high at idle. Technician B says PCV valve flow is high at cruising speed on a vehicle with an 8-cylinder engine. Who is correct?
Neither Technician is correct. When manifold vacuum is high (at idle, cruising and light-load operation), the PCV valve restricts the airflow to maintain a balanced air-fuel ratio. Under high speeds or heavy loads, the PCV valve opens to allow maximum flow.
Technician A says a digital voltmeter cannot be used to check an 02 sensor. Technician B says a test light can be used to check an 02 sensor. Who is correct?
Neither Technician is correct. When testing an oxygen sensor, a digital voltage meter or oscilloscope are the best choices. A scan tool can also be used.
Technician A says the normal secondary-circuit resistance of an ignition coil is low (5 ohms or less). Technician B says the spark plug wire is a secondary component that should have a resistance of 20,000 ohms or more per foot. Who is correct?
Neither Technician is correct. When testing the resistance of an ignition coil, the primary circuit should be around 1 to 3 ohms; however, some coils have an even lower specification. The secondary circuit resistance should be around 9,000 to 30,000 ohms depending on the manufacturer. Spark plug wires should be visually inspected and their resistance checked. Resistance is usually less than 10,000 ohms per foot.
When installing and timing the distributor, Technician A says the engine must be timed referencing TDC on the specified cylinder's exhaust stroke. Technician says if the engine is timed on the compression stroke, then the distributor will be 180 degrees off. Who is correct?
Neither Technician is correct. When timing the distributor, piston #1 is brought to TDC on the compression stroke, then the distributor is installed. Once started, the ignition timing must be set using a timing light.
Technician A says that for non-emissions-related DTCs, you can replace the component without using the flow chart. Technician B says depending on the DTC set, some steps of the flow chart can be bypassed. Who is correct?
Neither Technician is correct. When troubleshooting diagnostic trouble codes, a diagnostic flow chart should be used to ensure proper diagnostics.
While testing the secondary ignition with an oscilloscope, which of the following is the LEAST LIKELY cause of high resistance in the ignition secondary circuit?
No dielectric grease on the ignition module mounting surface: The lack of dielectric grease on the back of an ignition module will cause the module to overheat, but will not increase the secondary resistance.
Technician A says a scan tool can be used to check for oxygen sensor codes and operation. Technician B says. The oxygen sensor can be removed and tested under for proper operation. Who is correct?
Only Technician A is correct. A scan tool can be used to monitor the operation of the 02 sensors on a vehicle. The voltage is monitored and should be switching back and forth between 100 millivolts and 900 millivolts.
Technician A says a scan tool or code reader is used to retrieve DTCs from an OBD II vehicle. Technician B says the DTCs can be retrieved by watching and counting the number of flashes from the ma1riinctionin indicator lamp (MIL) on OBD II vehicle. Who is correct?
Only Technician A is correct. A scan tool or code reader must be used to retrieve DTCs from an OBD II vehicle.
Technician A says blue smoke in the exhaust indicates oil being burned in the combustion chamber. Technician B says white smoke in the exhaust indicates a rich air/fuel ratio. Who is correct?
Only Technician A is correct. A vehicle that is burning oil will have a blue to gray color to the exhaust.
Technician A says if an engine uses low-resistance injectors with less than 3 ohms resistance, then the PCM will use a current-limiting or peak and hold injector driver to operate the fuel injector. Technician B says using a current-limiting or peak and hold injector increases fuel injector noise. Who is correct?
Only Technician A is correct. An injector with less than 3 ohms resistance will be controlled with a current-limiting or peak and hold injector driver.
Technician A says that an oscilloscope can be used to watch the mass air flow (MAF) sensor signal switch from idle to wide-open throttle (WOT) status. Technician B says fuel injectors can only be tested using an ohmmeter. Who is correct?
Only Technician A is correct. An oscilloscope is used to test the operation on the MAF. Depending on what type of MAF sensor is used, it will produce a digital signal or a frequency.
Technician A says that during a cylinder compression test, low readings on adjacent cylinders may be caused by a cracked cylinder head. Technician B says a low reading on a single cylinder that increases when a tablespoon of oil is added is probably a valve problem. Who is correct?
Only Technician A is correct. Any time adjacent cylinders are both low, a blown head gasket or cracked head should be suspected.
Technician A says a fault throttle position sensor (TPS) can cause a dead spot in the throttle when accelerating. Technician B says faulty TPS will always set a DTC. Who is correct?
Only Technician A is correct. As a TPS wears, it can develop an open spot in it were it rides the most. When driving a vehicle with a bad spot in the TPS, the vehicle will have a dead spot in the throttle when the bad portion of the TPS is reached.
Technician A says with the PCV valve disconnected from the rocker cover, there should be vacuum at the valve with the engine idling. Technician B says when the PCV valve is removed and shaken, there should not be a rattling noise. Who is correct?
Only Technician A is correct. At idle with the PCV valve removed from the valve cover, there should be vacuum at the PCV valve.
Technician A says that cranking the engine with the throttle fully depressed will force a lean mixture to clear a flooded engine on some vehicles. Technician B says that high system voltage will increase fuel injector on time (pulse width). Who is correct?
Only Technician A is correct. Depressing the throttle fully during cranking ill make the computer enter clear flood mode and lean out the air/fuel mixture on some vehicles.
Technician A says if the PCV valve is stuck closed, then excessive crankcase pressure forces blowy gases through the clean air hose into the air filter. Technician B says if the positive crankcase ventilation (PCV valve is stuck open. then excessive airflow through the valve causes a rich air/fuel ratio. Who is corrects
Only Technician A is correct. If the PCV valve were to stick closed, then excessive blow-by gases would build in the engine, forcing those gases (and often oil) through the air cleaner hose and into the air filter.
A multi-trace oscilloscope is being used on the pre- and post-catalytic converter heated oxygen sensors, and the results are shown as illustrated. Technician A says the catalytic converter is working correctly. Technician B says the post-converter heated 02 sensor should be replaced. Who is correct?
Only Technician A is correct. If the catalytic converter (CAT) is working correctly, then the pre-CAT heated oxygen sensor will have normal switch between 900 millivolts and 100 millivolts just as illustrated.
Technician A says a stuck-open purge control valve could cause a hesitation on takeoff. Technician B says the purge control valve is a normally open solenoid. Who is correct?
Only Technician A is correct. If the purge solenoid were to stick open, then the canister would be purging all the time causing the engine to run too rich. This could cause a hesitation.
Technician A says that special fuel injection hose must be used when replacing the fuel lines on a fuel-injected vehicle. Technician B says the fuel supply hose is usually smaller than the fuel return hose. Who is correct?
Only Technician A is correct. Regular fuel hose cannot be used on a fuel injected vehicle. Fuel injection produces higher pressures than an old carbureted system, so the hose must be rated as fuel injection hose.
Technician A says that turning off fuel injectors at high RPM is the purpose of the rev limiter—to protect the engine from damage or limit vehicle speed. Technician B says that turning off fuel injectors while the engine is running must be done at speeds above 45 mph. Who is correct?
Only Technician A is correct. The rev limiter is used to protect the engine from over revving. Rev limiters are set at different RPMs depending on manufacturer.
Technician A says the secondary ignition circuit is designed to handle high voltages up in the thousand volts. Technician B says the secondary circuit produces dangerously high amperage. Who is correct?
Only Technician A is correct. The secondary ignition system is designed to handle very high voltages, some as high as 70,000 or 80,000 volts.
Technician A says the thermostatic coil controls the opening and closing of the orifice inside the coupling on a viscous fan clutch. Technician B says when the thermostatic coil is cold, the orifice is open on a viscous fan clutch. Who is correct?
Only Technician A is correct. The viscous fan clutch is designed to give maximum airflow when hot and minimum air flow when by opening and closing a orifice inside the viscous clutch.
Technician A says the best way to clear diagnostic trouble codes is to remove the battery negative terminal for five seconds. Technician B says the monitor for the repaired system should be performed before the vehicle is returned to the customer. Who is correct?
Only Technician B is correct With On-Board Diagnostics II (OBD II), the repair can be confirmed by driving the vehicle through the necessary drive cycles, running the system monitor on the system that was repaired.
During a vacuum test the vacuum gauge shows a rapidly fluctuating motion from 15 to 21 in. Hg at idle. Technician A says this could be caused by a loose intake manifold. Technician B says this could be caused by a burned exhaust valve. Who is correct?
Only Technician B is correct. A burnt valve would cause the needle on the vacuum gauge to rapidly fluctuate between 15 and 21 in. Hg.
An SFI engine has poor acceleration when the vehicle is suddenly accelerated to wide-open throttle. Idle and cruise performance is line. Technician A says a faulty mass airflow sensor could cause this. Technician B says a weak fuel pump could cause this. Who is correct?
Only Technician B is correct. A weak fuel pump could cause poor acceleration when suddenly going to WOT.
A vehicle with DTC code P0304 (Cylinder #4 Misfire) is being diagnosed. Technician A says high fuel pump pressure could be the cause. Technician B says an open spark plug wire could be the cause. Who is correct?
Only Technician B is correct. An open spark plug wire, fouled spark plug, or shorted spark plug would all cause a misfire code.
A 6-cylinder engine is making a loud metallic knocking that gets louder as the engine warms up or if the throttle is quickly snapped open. The noise almost disappears when the spark for cylinder #2 is shorted to ground. Technician A says the problem could be a cracked flex plate. Technician B says the problem is most likely a loose connecting rod bearing. Who is correct?
Only Technician B is correct. If a knock gets quieter when the spark is shorted for the cylinder with a loose rod bearing, then the rod bearings are most likely the cause.
Technician A says the plug wire resistance should not exceed 10 megohms of resistance. Technician B says plug wire insulation can be checked with a saltwater solution in a spray bottle. Who is correct?
Only Technician B is correct. If the spark plug wire insulation breaks down, then the spark can ground at other areas besides the spark plug. To check for this problem, spray a saltwater solution along the spark plug wire. If an arc is found, then the spark plug wire should be replaced.
Technician A says the PCM cannot be harmed with static electricity if the negative and positive battery cables are disconnected. Technician B says you should always ground yourself to the vehicle while working on a PCM. Who is correct?
Only Technician B is correct. It is always good practice to ground yourself with the vehicle before removing the PCM, this can be done using a special wrist grounding strap.
Technician A says that the resistance in the power side of the power distribution circuit cannot be over 200 ohms of resistance. Technician B says the power side of the power distribution circuit can be voltage-drop tested to check the circuit for resistance. Who is correct?
Only Technician B is correct. Performing a voltage drop test is the best way to check for excessive resistance in an electrical circuit. Anything over 0.5 volts is considered high.
Technician A says that the first step of any diagnostic procedure is to check for DTCs. Technician B says the search for technical service bulletins (TSB) should be consulted before any repairs are made. Who is correct?
Only Technician B is correct. Sometimes the fix is as simple as performing a procedure found in a technical service bulletin. If a vehicle has the same symptoms described in a TSB, then the TSB instructions should be performed before further repair is made.
Technician A says a diagnostic trouble code (DTC) tells you which component is malfunctioning. Technician B says if a fault exists that affects emissions, then the malfunction indicator lamp (MIL) will be illuminated. Who is correct?
Only Technician B is correct. The MIL will illuminate any time a failure of a circuit or system occurs that causes the vehicle to emit emissions 1.5 times the federal test procedure allowance.
Technician A says most computer inputs are received from other computers. Technician B says one input might affect other computers. Who is correct?
Only Technician B is correct. The PCM, BCM, and anti-lock brake module may all share information from one input sensor.
Technician A says if the positive crankcase ventilation (PCV) valve rattled when shaken, then the PCV system is OK. Technician B says the PCV system vents excess pressure formed in the crank case from piston blow-by. Who is correct?
Only Technician B is correct. The PCV system is used to vent excess pressure in the crankcase through the engine. The excess pressure develops when compression pressures escape past the piston rings on the compression stroke. An inoperative PCV system can lead to oil leaks, premature gasket, and seal failure.
Technician A says that when vacuum is applied to the EGR valve with the engine idling, the EGR valve should open and idle should increase. Technician B says that a diagnosis of the EGR valve should be done with the engine idling. Who is correct?
Only Technician B is correct. The best engine speed to test an EGR system is at idle. Testing the EGR valve at a higher engine RPM might hide the problem.
Technician A says valve adjustment should always be performed on a cold engine. Technician B says the piston should be placed at top dead center (TDC) of the compression stroke. Who is correct?
Only Technician B is correct. The correct piston position for valve adjustment is at TDC on the compression stroke. This ensures the valves are closed completely.
Technician A says performing a fuel pressure test confirms proper operation of the fuel injector. Technician B says it is possible to have an electrical problem with an injector, even though the fuel pressure drop is within specifications. Who is correct?
Only Technician B is correct. The fuel pressure drop test is used to check fuel flow through the injector, not the electrical circuit. The injector must be checked for resistance to check the electrical function.
A vehicle needs to have its PCM re-flashed. Technician A says the vehicle should be left running to prevent accidental battery discharge during flashing. Technician B says the scan tool must fit in the DLC snuggly. Who is correct?
Only Technician B is correct. When re-flashing a PCM, the old program is erased and a new one installed. If the battery runs down or the scan tool comes loose from the DLC, then all information could be lost to the point that communication with the PCM cannot be reestablished and a new PCM must be purchased.
A DTC for an intake air temperature sensor may be set by any of the following conditions EXCEPT:
Operating the vehicle in extremely cold climates: Operating the vehicle in extremely cold weather will not cause a DTC to be set.
What term describes the condition when the air/fuel mixture is ignited before the spark plug is fired?
Pre-ignition: Pre-ignition occurs when a hot spot in the combustion chamber causes the air/fuel mixture to ignite before the spark is delivered to the spark plug.
Which of the following is the most likely cause of ignition coil failure?
Prolonged open circuit in the secondary: An open in the secondary circuit can cause internal tracking in the ignition coil, causing premature coil failure.
All of the following are part of the diagnostic process EXCEPT:
Re-flash the PCM:
Which of the following is the LEAST LIKELY cause of a fuel tank leak?
Retaining straps: Fuel tank retaining straps are very seldom the cause of fuel tank leaks.
A seized-up turbo charger can cause vacuum readings to do which of the following?
Show a continuous gradual drop as engine speed is increased: A seized-up turbocharger can create a restricted exhaust which will cause the vacuum to continuously and gradually drop as the engine speed is increased.
All of the following are measured by a 5-gas analyzer EXCEPT:
Smog: Smog is a photochemical mixture of gases that cannot be measured with a 5-gas analyzer.
All of the following are components of the primary circuit EXCEPT:
Spark plug wire: The spark plug wire is a secondary ignition component; secondary ignition components handle high voltage (20,000—50,000 volts) and primary handle low voltage (12 volts).
All of the following are part of reprogramming the PCM EXCEPT:
Start the engine for 15 seconds: The reprogramming procedure is performed with the key on and the engine off.
All of the following symptoms can be caused by low fuel pressure EXCEPT:
Strong sulfur smell from the exhaust: A strong sulfur smell from the exhaust is a symptom of a rich mixture. Low fuel pressure would cause a lean mixture.
Which of the following conditions is most likely caused by a manifold absolute pressure (MAP) sensor?
The MAP sensor is used for load detection, a bad MAP sensor can definitely cause poor fuel economy complaints.
All of the following components are part of the fuel pump control circuit EXCEPT:
The ignition switch supplies the power to the PCM and the fuel pump relay.
What is the purpose of coating the back of an ignition module with heat sink grease (sometimes referred to as dielectric silicone crease before installation?
To help dissipate heat from the module: The dielectric grease helps transfer the heat generated in the ignition module away from the module.
All of the following conditions could result in a voltage drop in a circuit EXCEPT:
Using dielectric grease in a connector: Dielectric grease is used in a connector to protect it from moisture, but will not cause a voltage drop.
A cylinder-power balance test on a distributor-ignition vehicle can indicate all of the following problems EXCEPT:
Weak ignition coil: A weak coil would affect all the cylinders, so a power balance test would not help find it.
An evaporative system DTC may be set by all of the following EXCEPT:
While the EVAP system prevents hydrocarbons (HCs) from entering the atmosphere, it cannot detect a leaking fuel injector.
All of the following could cause a cylinder misfire diagnostic code to be set EXCEPT:
Worn cam shaft lobe: The misfire monitor reads the crankshaft signal to determine a miss. A cylinder that is missing will cause the engine to slow down when that cylinder is supposed to fire. A worn cam lobe will not cause the engine to slow down.
Which of the followings is the most likely cause of blue exhaust smoke?
Worn piston rings: Worn piston rings allow oil to leak into the combustion chamber, where it burns, developing a blue-colored exhaust smoke.
Which of the following is most likely to cause a double-knocking noise with the engine at an idle?
Worn piston wrist pins: Worn piston wrist pins create a double-knock because the piston changes direction at TDC (top dead center) and BDC (bottom dead center) every crankshaft revolution.
When diagnosing a fuel injection system problem, a technical service bulletin search is performed for all of the following reasons EXCEPT:
Year, make, and vehicle identification number: The year, make and vehicle identification number should already be known before doing a TSB search.