Powertrain

On a 2001 model year or newer vehicle, the PCM is required to turn on the MIL and store a DTC if an EVAP system leak is identified that is larger than:

0.020 in

What is the operating voltage of the Honda IMA mild hybrid system?

144 volts

In a GDI system the fuel injectors spray fuel directly into the combustion chamber and require higher fuel pressures under heavy load, typically as high as

2,140 PSI

An OBD II PCM will erase confirmed DTCs from memory if it does not see the problem occur again for:

40 warm-up and cool-down cycles of the engine

What voltage will be produced by a zirconia O2 sensor when the air-fuel ratio is on the rich side of stoichiometric?

450 mV to 900 mV

In the figure above, if there was an open at terminal "C", what would the voltage signal to the PCM be?

5 volts

With modern terminology, the acronym "DI" refers to which type of ignition system?

A distributor ignition system using only one ignition coil

The image below shows the typical form of a flowchart, or "troubleshooting tree." Which of the statements is true about a flowchart?

A flowchart shows steps to take to make a pinpoint test or tests in response to a particular DTC

Which statement about advantages and disadvantages of certain diagnostic tools is true?

A logic probe is safer to use on electronic systems than a non-powered test light.

Which condition could cause a circuit's fuse to burn open due to excessive current flow?

A shorted winding within a load component

Which characteristic(s) describe advantages of multiplexed circuits over hard-wired circuits?

All of the above a. Elimination of wiring and wiring connectors, thus reducing vehicle weight while adding reliability b. Lower cost to manufacture c. Increased computer diagnostic abilities

Which statement(s) is/are true concerning GM vehicles with the Allison two-mode hybrid technology?

All of the above a. They have an EMG that is designed to offer an advantage in fuel economy at city speeds. b. They have an EMG that is designed to offer an advantage in fuel economy at highway speeds. c. They use AFM technology to offer an advantage in fuel economy during cruise conditions.

Which statement(s) about exhaust gas analyzers and the gases they measure is/are true?

All of these a. Four-gas analyzers measure HC, CO, CO2 and O2. b. Five-gas analyzers measure the same gases as four-gas analyzers plus nitrogen oxides (NOx). c. Exhaust gases are greatly affected by the air-fuel ratio. (The stoichiometric air-fuel ratio is 14.7:1; a rich ratio has more fuel; a lean ratio has more air).

A data stream is data delivered from the PCM to a scan tool. The parameter ID (PID) identifies the specific type of information being delivered, for example:

All of these a. Fuel trim numbers b. Input voltages c. Memory DTCs

The catalytic converter, located in the exhaust system, causes low-temperature oxidation of hydrocarbons (HC) and carbon monoxide (CO) and reduction of nitrogen oxide (NOx). Which of the following correctly states the harmless gases that result from each toxic emission?

All of these a. Hydrocarbons (HC) become water (H2O) and carbon dioxide (CO2). b. Carbon monoxide (CO) becomes carbon dioxide (CO2) . c. Nitrogen oxide (NOx) becomes nitrogen (NO2) and oxygen (O2).

The gasoline direct injection (GDI) system sprays fuel directly into the combustion chamber, creating a finely atomized fuel spray that results in more power from less fuel. It also uses a lean air-fuel charge during cruise and some use turbochargers that further increase performance and fuel economy. However, GDI systems do have drawbacks, such as

All of these a. On the high-pressure side of the system, the PSI at idle will split human skin is a safety concern. b. The high voltage initially applied to the fuel injectors is a safety concern. c. Carbon tends to build up on the back side of the intake valves, restricting air flow into the chamber.

Which statement(s) about concentration sampling is/are true?

All of these a. With engine running, a probe is inserted into the exhaust pipe to take a small sample from the total exhaust gas volume. b. The portion of each gas within the sample is measured, with each measurement expressed either as a percentage (parts-per-hundred) or as parts-per-million (PPM). c. Concentration sampling is usually done in the shop with the vehicle at idle; a dynamometer or portable gas analyzer can monitor emissions levels while the vehicle is being driven.

The computer is programmed to keep the system in closed loop as much as possible because it is the most efficient mode of operation. However, the system will not go into closed-loop operation until:

All of these, A predetermined time elapses from when the engine was started, The oxygen sensor reaches operating temperature, The engine coolant temperature reaches a criterion temperature.

A stoichiometric air-fuel ratio is one in which:

All of these, All the fuel and all the O2 in the cylinder are consumed during combustion, The air-fuel mixture is neither lean nor rich, The least amount of toxic emissions leave the combustion chamber.

Which of the following statements is/are correct about a solenoid-operated valve?

All of these, It consists of a coil of wire around an iron core with a valve at the end., When the computer grounds the solenoid circuit, current flows through it., Current through the wire coil creates a magnetic field that moves the iron core and valve.

Which of the following statements is/are correct about a stepper motor?

All of these, It is a small electric motor powered by pulses of voltage, The computer pulses current to the motor's coils to turn the motor a certain number of degrees, The computer can reverse the sequence to turn the motor in the opposite direction.

The Greek letter lambda (λ) represents the air-fuel ratio. Which of the following statements is correct regarding lambda values?

All of theses a. At the stoichiometric air-fuel ratio 14.7 parts of air to 1 part of fuel, lambda equals 1. b. An air-fuel ratio 4% richer than 14.7:1, lambda is 0.96. c. An air-fuel ratio 3% leaner than 14.7:1, lambda is 1.03.

What requirement(s) is/are mandated by OBD II?

Both All manufacturers must redesign their engine control systems so as to operate identically in all respects and according to an EPA-designed engine control system. The PCM must turn on the MIL if component and/or system inefficiency results in emission levels exceeding two times the FTP cut-point.

What ratings has the 2004 Prius with THS-II earned that the original Prius did not earn?

Both ULEV AT-PZEV

Emissions that escape during refueling are being discussed. Technician A says an on-board refueling vapor recovery system may be used. Technician B says a fuel tank bladder may be used. Who is correct?

Both A and B

Technician A says on pulse width modulated (PWM) busses, all bits are the same length. Technician B says on variable pulse width (VPW) designs, one pulse may be long and the next pulse may be short. Who is correct?

Both A and B

Technician A says that a diode is an electrical one-way check valve with no moving parts. Technician B says that a transistor is an electronic switch with no moving parts. Who is correct?

Both A and B

Everything that goes into the engine combustion chamber is ultimately expelled from the tailpipe. Which statement about what goes into the combustion chamber is true?

Both atmospheric air and fuel are introduced into the engine's combustion chamber.

Which statement(s) is/are true about preparing the gas analyzer before the vehicle is tested?

Both of these a. Before each test, the probe should be left open to sample ambient air. HC, CO, and CO2 should read very close to zero. b. O2 levels in the ambient air should read between 20% and 21%. If they do not, the oxygen sensor in the analyzer should be replaced.

The powertrain control module (PCM) uses closed-loop control to achieve a stoichiometric air-fuel ratio because:

Both of these, At this air-fuel ratio, the engine produces the smallest amount of toxic emissions and maximizes production of nontoxic emissions. At this air-fuel ratio, the catalytic converter operates at its peak efficiency.

Technician A says one advantage of a variable valve timing system is that it allows a higher-compression engine to burn a lower octane fuel while still being able to control the potential for detonation. Technician B says that most VVT systems use engine oil pressure to control them hydraulically. Who is correct?

Both technicians

Technician A says that closed loop is the most efficient operating mode and allows the engine computer to control the air-fuel ratio with the most precision. Technician B says that open loop operation is used to improve performance during cold engine warm-up and is also used under heavy load or during wide open throttle operation. Who is correct?

Both technicians

Technician A says that if a relay is normally open, it must be energized in order to complete the controlled circuit. Technician B says that if a solenoid-operated valve is normally closed, it must be energized in order to allow flow through it.Who is correct?

Both technicians

The PCM will compare input values to each other when running which OBD II monitor?

Comprehensive Components Monitor

A modern catalytic converter in good working order and up to proper operating temperatures will effectively oxidize HC and CO emissions, converting them to nontoxic gases—which is all the technician needs to know about a vehicle's exhaust gases.

False

A relay is a remote-control switch that can be N/O (normally open) or N/C (normally closed). Current flows when the relay is open, does not flow when the switch is closed.

False

A solenoid circuit can be turned rapidly on and off. If a solenoid is always turned on for 20 percent of each tenth of a second and off for 80 percent of that time, it is said to be operating on an 80 percent duty cycle.

False

An analog voltage is either fully on or fully off, never in between—while a digital voltage varies between the on/off extremes.

False

Auto mechanics may occasionally open the PCM computer's housing to clean or repair internal components.

False

Fuel volatility (ability to vaporize) is important because only liquid fuel burns in the cylinder while fuel vapor exits the cylinder unburned.

False

In all cases, the ideal air-fuel ratio is 14.7:1

False

In order to ease cold weather starting, gasoline refiners produce gasoline in the winter months that has a:

Higher volatility

Which function is likely to be controlled by a body control module (BCM)?

Interior lights

Most often, how does the PCM energize an output actuator?

It completes the actuator's ground path

Which of the following best describes how a permanent magnet sensor operates?

It generates an AC voltage signal

Which of the following sensors may be used in place of the speed density formula?

MAF sensor

On GM OBD II vehicles, the PCM tests EGR operation by turning EGR on and off and monitoring which of the following sensors?

MAP sensor

In an evaporative and canister purge system, which of the following is not a potential problem?

NOx emissions tend to escape from the charcoal canister.

Which of the following statements is true about a pinpoint test?

None of these a. A DTC produced by the PCM will pinpoint the exact fault that must be repaired. b. The PCM will describe the repair that must be made to correct the DTC. c. PCMs make it possible to pinpoint and repair faults quickly and easily.

The PCM will purposefully pulse the fuel injectors abnormally rich and lean when running which OBD II monitor?

O2 Sensor Monito

Which of the following sensors cannot produce or generate a voltage signal?

Potentiometer

Which of the following types of sensors cannot be used as a RPM reference sensor?

Potentiometer

A standardized binary code (or computer language) is known as a:

Protocol

With the engine running, how is the PCM programmed to pulse the fuel injectors in a sequential fuel injection (SFI/SMPI) system?

Pulse the injectors individually in the engine's firing order

Solid-state electronics—for example, computers and amplifiers—control complex systems without having any moving parts. The basis of solid-state electronics is the:

Semiconductor

To know how much fuel to meter into the cylinder to achieve the desired air-fuel ratio, the microprocessor must know much air is in the cylinder. Many systems use a mathematical calculation that considers all the factors (engine parameters) that affect how much air gets into the cylinders. This mathematical calculation is called the

Speed density formula

The two types of electric motors used as actuators are:

Stepper motors and permanent magnet field motors.

What should you do when testing a knock sensor?

Tap it lightly with a metallic object while measuring the output

Technician A says that voltage drop occurs in a circuit only when the circuit is complete and current is flowing. Technician B says that amperage is reduced as it passes through a series circuit. Who is correct?

Technician A only

Two technicians are discussing how to test a permanent magnet vehicle speed sensor.Technician A says that you should test the coil's resistance and compare it to specification. Technician B says that you should set your DVOM to the "DC volts" scale to test the sensor's ability to produce voltage. Who is correct?

Technician A only

Exhaust gasses are being discussed. Technician A says nitrogen (N) is considered a harmful gas. Technician B says carbon monoxide (CO) is considered a harmful gas. Who is correct?

Technician B only

Technician A says that a PCM uses an output actuator to keep itself informed of engine operating conditions. Technician B says that a PCM uses an output actuator to cause a change in the performance of a circuit or system. Who is correct?

Technician B only

The OBD II data link connector (DLC) is being discussed. Technician A says terminal fourteen is always battery positive. Technician B says terminals four and five are always grounds. Who is correct?

Technician B only

The bus-H and bus-L circuits of a dual wire (DW) bus used on a Ford are being viewed on a dual-channel oscilloscope. Technician A says the waveforms should be identical. Technician B says the waveforms should mirror each other. Who is correct?

Technician B only

Which of the following statement(s) is/are true about homogeneous charge compression ignition (HCCI) engines?

The HCCI engine uses heat to auto-ignite the air-fuel charge without the use of a spark plug.

In addition to flashing the MIL, how do many OBD II PCMs react to a "Type A" (severe) cylinder misfire?

The PCM turns off the fuel injector for the misfiring cylinder.

How do manufacturers reduce the effects of an induced voltage in a single-wire (SW) multiplexed circuit?

The modules communicate with digital on/off signals that have a slight angle at the edges (are trapezoidal in shape).

How will an increase in temperature from 50oF to 220 oF affect the resistance of an NTC thermistor?

The resistance decreases

What does the term baud rate mean?

The speed of communication

Which of the following is NOT required in order for an engine computer to enter closed loop operation?

The vehicle must be at or above a designated speed as measured by the vehicle speed sensor.

In the figure above, as the engine coolant temperature sensor's resistance decreases, how will the voltage signal to the computer change?

The voltage signal decreases

Which of the following statements is true regarding an ignition coil?

The voltage spike is induced only when the current flow is turned off.

On an OBD II vehicle, following the illumination of the MIL, the MIL will stay lit until the system or component passes the same test for _____ consecutive trips.

three

Water vapor (H2O), carbon dioxide (CO2) Oxygen (O2), and nitrogen (N2) are nontoxic exhaust gases. Hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NO2) are toxic exhaust gases.

True

When using gas analysis to aid in diagnosing engine performance problems, fuel economy problems, or emission test failures, the technician should record the readings of all gases at both idle and at 2,500 RPM.

True

On an OBD II vehicle, how many times must the PCM see a fault present before it will illuminate the MIL (for most faults)?

Two

During vehicle diagnosis, you discover that the scan tool will not communicate with the network. All of these checks should be made EXCEPT:

Use a lab scope to interpret the data on the bus

Open-loop operation is:

Used when a stoichiometric air-fuel ratio is not appropriate.

Which acronym applies to serial data in which the "ones" and "zeros" are defined not only by the voltage value but also by the bit length (a "one" can be a short high-voltage pulse or a long low-voltage pulse and a "zero" can be a short low-voltage pulse or a long high-voltage pulse)?

VPW

Reid Vapor Pressure (RVP) is a unit of measurement used to measure a fuel's:

Volatility

In manufacturer's recommendations for disconnecting the HV battery of hybrid electric vehicles, the following procedures are typically recommended EXCEPT:

being sure to wear high-voltage Shepherd's gloves

An OBD II PCM is able to detect engine misfire by monitoring:

engine RPM

During closed-loop operation of a fuel injection system, the PCM is programmed to perform all of the following functions EXCEPT:

fine-tuning the air-fuel ratio to minimize toxic emissions while maximizing fuel economy

The computer that is the dominant node on the bus and controls the data bus is known as the _____.

master node

48 V systems are being introduced on dual voltage vehicles in which some parts of the vehicle use the higher voltage while most of the vehicle's systems still operate at 14 V.

True

A wideband O2 (WBO2) sensor is able to measure air-fuel ratio across a much broader spectrum than standard zirconia and titania O2 sensors.

True

Active command is a type of functional test the PCM will perform in response to a command from a technician, but the PCM does not deliver a pass/fail analysis of the information it produces; that determination is up to the technician.

True

Closed-loop operation means that the engine computer monitors the results of its own control actions through a feedback circuit.

True

Crankshaft position sensors monitor the position of the crankshaft; camshaft position sensors monitor the position of the camshaft.

True

Fuel injectors are solenoid-operated valves that are spring-loaded normally closed (N/C) and spray fuel when electrically energized by the computer.

True

Fuel trim is a PCM function that makes adjustments to the fuel-injector's pulse width to maintain an acceptable air-fuel ratio. The technician can use a scan tool look at both short-term and long-term values as a diagnostic aid.

True

In a returnless fuel-injection system, excess fuel reaches the engine but is not returned to the fuel tank.

True

In a speed-density application, the computer calculates how much air enters the engine. By contrast, a hot-wire mass air flow (MAF) sensor actually measures the amount of air that enters the engine.

True

The first important thing in interpreting an electrical schematic (map of an electrical system showing components, wires, circuits, connectors, and terminals) is to identify the components.

True

The fuel injection systems of all vehicles currently manufactured in the U.S., Europe, or Asia have these two features in common: (1) The amount of fuel metered into the engine by the PCM depends on how much air is entering the engine. (2) The PCM meters the appropriate amount of fuel into the engine using one of four major fuel injection systems.

True

The two types of faults that may occur in an automotive computer system are hard faults (ones that are currently present) and soft faults (ones that are intermittent).

True

Why should a DSO be used in diagnosing a vehicle's multiplexing bus?

To check for the presence of serial data (binary code) when a scan tool fails to communicate

In addition to providing voltage to the computer's internal circuits, what is the purpose of the reference voltage regulator within a modern PCM?

To provide 5 volts to the sensors on the input side of the PCM

What is the primary purpose for replacing 14-volt systems with 42-volt systems?

To provide more total wattage than a 14-volt system can provide

Why are the two wires of a twisted-pair multiplex system twisted?

To reduce the effects of induced voltage