Engine Performance Final
When checking the ECT sensor with a scan tool, about what temperature should be displayed if the connector is removed from the sensor with the key on, engine off?
-40°F (-40°C)
Typical TP sensor voltage at idle is about ________.
0.5 volt or 10% of WOT sensor voltage
Which sensor produces a square waveform?
Hall-Effect sensor
A reluctor is a ________.
Notched ring or pointed wheel
Typical secondary coil resistance specifications usually range from ________ ohms
6,000 to 30,000
A typical IAT or ECT sensor reads about 3000 ohms when tested using a DMM. This resistance represents a temperature of about ________.
70° F (20°C)
The throttle plate actuator motor is what type of electric motor?
DC motor
When measuring the output signal of a MAP sensor on a General Motors vehicle, the digital multimeter should be set to read ________.
DC volts
The ETC actuator motor is controlled by the PCM through what type of circuit?
H-bridge
A P0118 DTC is being discussed. Technician A says that the ECT sensor could be shorted internally. Technician B says that the signal wire could be open. Who is right?
Technician B only
Which can be used to test for a fault with a cylinder on a waste-spark system?
Using short sections of rubber hose attached to the coil terminals
What unit of electricity is used as a signal for a computer?
Volt
Which computer function describes how the computer handles inputs?
Process
The pulse generator ________.
Signals the electronic control unit (module)
What are the two methods of sensing incoming engine air flow?
Speed density and mass air flow
After a TP sensor has been tested using the min/max function on a DMM, a reading of 5 volts is displayed. What does this reading indicate?
TP sensor is shorted TP sensor signal shorted to 5v reference
A P0122 DTC is retrieved using a scan tool. This DTC means ________.
TP sensor signal circuit short-to-ground TP sensor voltage is low TP sensor short-to-ground
Which term describes the process of manually adjusting variables such as speed, load, and spark timing to determine the optimum output settings for the computer?
Engine mapping
A waste-spark-type ignition system ________.
Fires two spark plugs at the same time Fires one spark plug with straight polarity Fires one spark plug with reverse polarity
The accelerator pedal position sensor uses two or three separate sensors that output a varying voltage signal. What is the purpose of using more than one sensor?
For safety reasons Improves redundancy Allow the computer to detect a malfunction
Which type of sensor uses a burn-off circuit?
Hot wire MAF sensor
Which of these sensors does the TP sensor back up if the PCM determines that a failure has occurred?
MAP or MAF sensor
The SAE term for the vehicle computer is ________.
PCM
A TP sensor is what type of sensor?
Potentiometer
What type of sensor is used to measure the position of the throttle?
Potentiometer
If the MAF sensor fails, the PCM uses ________ to calculate fuel delivery needs.
RPM and throttle position
Which item is a computer input sensor?
RPM, throttle position, engine coolant temperature
Which wire on a typical TP sensor should back-probed to check the voltage signal to the PCM?
Signal wire
The primary (low-voltage) ignition system must be working correctly before any spark occurs from a coil. Which component is NOT in the primary ignition circuit?
Spark Plug Wires
What part of the scope pattern show the duration of the spark?
Spark line
What should be inspected as part of a visual inspection of the ignition system?
Spark plug wires for proper routing
How does a waste-spark ignition system fire the spark plugs?
The same plug always is fired straight or reverse polarity
With the ignition off and the key out of the ignition, what should happen if a technician uses a screwdriver to gently push on the throttle plate in an attempt to open the valve?
The throttle should move, and then spring back to the home position when released.
What two things can a vehicle computer actually perform (output)?
Turn something on or turn something off
The four basic computer functions include ________.
input, processing, storage, and output
To what extent is the throttle plate spring loaded to hold the throttle slightly open?
16% to 20%
Most TP sensors have how many wires?
3
The typical MAF reading on a scan tool with the engine at idle speed and normal operating temperature is ________.
3 to 7 grams per second
A typical TP sensor registers about how many volts at WOT (wide open throttle)?
4.5
What type is the throttle position sensor used in the throttle body assembly of an ETC system?
A Hall-effect sensor Two potentiometers that read in the opposite direction
A green wrench symbol is displayed on the dash. What does this mean?
A fault in the ETC in a Ford has been detected.
Analog signals from sensors are changed to digital signals for processing by the computer through which type of circuit?
Analog-to-digital converter
Which of these tools would be used to test a MAP sensor?
A digital voltmeter
If the transmission fluid temperature (TFT) sensor indicates cold automatic transmission fluid, what would the PCM do to the shifts?
Delayed shift points and torque converter clutch disabled
Coil polarity is determined by the ________.
Direction of rotation of the coil windings
HEI and EIS are examples of ________.
Distributor ignition systems
The sensor that most determines fuel delivery when a fuel injected engine is first started is the ________.
ECT sensor
What happens to the voltage measured at the ECT sensor when the thermostat opens?
Increases slightly
Which computer function is defined as a voltage signal from a sensor or switch?
Input
Which of the following components measures the volume and density of the incoming air?
Mass Air Flow Sensor
Which of these is NOT a purpose or function of the MAP sensor?
Measures engine speed
When testing the ECT sensor with the connector disconnected, the technician should select what position on the DMM?
Ohms
Technician A says that a heavy engine load results in high intake manifold vacuum and a high MAP sensor signal voltage. Technician B says that a manifold absolute pressure (MAP) sensor uses a perfect vacuum (zero absolute pressure) in the sensor to determine the pressure. Who is right?
Technician B only
Technician A says that an electronic throttle control uses a stepper motor. Technician B says that an electronic throttle control uses is spring loaded to about 16% to 20% throttle opening. Which technician is correct?
Technician B only
After a TP sensor has been tested using the min/max function on a DMM, a reading of zero volts is displayed. What does this reading indicate?
The TP sensor is open at one point during the test
A typical MAP sensor compares the vacuum in the intake manifold to ________.
a perfect vacuum
A spark tester should be used to check for spark because ________.
a spark tester requires at least 25,000 volts to fire
The use of an electronic control (ETC) system allows the elimination of all of these EXCEPT ________.
accelerator pedal
As engine speed increases, the timing of the spark in the cylinder must be ________,
advanced
Computer speed is measured in ________.
clock speed (Hz)
A COP ignition system can be called ________.
coil near plug, by plug, or over plug
The TP sensor affects the operation of all of these, EXCEPT ________.
correcting for rich and lean air-fuel mixtures
As the altitude of the vehicle increases, BARO voltage ________.
decreases
An engine fuel temperature (EFT) sensor is used on some vehicles, since fuel temperature changes the ________ of the fuel.
density
An ion-sensing ignition system allow the ignition system itself to be able to ________.
detect misfire, spark knock, and rich/lean mixture
The ratio of on time relative to the period of the complete cycle is the ________.
duty cycle
Air that enters the engine without passing through the air flow sensor is called ________.
false air
Which item is a computer output device?
fuel injector, transmission shift solenoid, and EVAP control solenoid
When the engine is at idle speed, manifold vacuum is ________.
high (17 to 21 in. Hg)
Poor engine performance could be the result of a ________.
high voltage spark leak defective coil ignition with the CMP and CKP not correctly indexed
As the load on an engine increases, manifold vacuum decreases and the manifold absolute pressure ________.
increases
Because of ________, an ignition coil cannot be fully charged (reach magnetic saturation) until after a delay of about 10 milliseconds.
inductive reactance
Typical primary coil resistance specifications usually range from ________ ohms.
less than 1 to 3
The ignition module has direct control over the firing of the coil(s) of an EI system. Which component(s) triggers (controls) the module?
pickup coil, computer, and crank sensor
When testing a MAP sensor, the technician should first check the ________ voltage.
reference
A fuel injection system that does not use a sensor to measure the amount (or mass) of air entering the engine is usually called a(n) ________ type of system
speed density
All of the following are approved methods or tools used when diagnosing an ECT (engine coolant temperature) sensor EXCEPT ________.
substituting a variable resistor
The spark plug threads in the cylinder head should be cleaned using a(n) ________ before installing new plugs.
thread chaser
The ignition system is usually divided into ________ different sections.
two
Which statement is FALSE?
Absolute pressure is equal to barometric pressure plus intake manifold vacuum.
A P0102 DTC is being discussed. Technician A says that a sensor circuit shorted-to-ground can be the cause. Technician B says that an open sensor voltage supply circuit could be the cause. Who is right?
Both technicians
A P0107 DTC is being discussed. Technician A says that a defective MAP sensor could be the cause. Technician B says that a MAP sensor signal wire shorted-to-ground could be the cause. Who is right?
Both technicians
Technician A says that MAP sensors use a 5-volt reference voltage from the PCM. Technician B says that the MAP sensor voltage will be higher at idle at high altitudes compared to when the engine is operating at near sea level. Who is right?
Both technicians
Technician A says that a MAF sensor actually measures the density and amount of air flowing into the engine. Technician B says a that hot wire MAF sensor uses the electronics in the sensor itself to heat a wire 70°C above the temperature of the air entering the engine. Who is right?
Both technicians
Technician A says that a defective spark plug wire can cause an engine misfire. Technician B says that a defective spark plug can cause an engine misfire. Who is right?
Both technicians
Technician A says that a defective spark plug wire or boot can cause an engine misfire. Technician B says that a tracked ignition coil can cause an engine misfire. Which technician is correct?
Both technicians
Technician A says that a pickup coil (pulse generator) can be tested with an ohmmeter. Technician B says that ignition coils can be tested with an ohmmeter. Who is right?
Both technicians
Technician A says that a two-wire COP system uses the PCM to trigger the coil. Technician B says that a three-wire COP system has an ignition module built into the coil assembly. Which technician is correct?
Both technicians
Technician A says that the ECT and IAT sensors can be tested visually, as well as by using a digital multimeter or a scan tool. Technician B says that the ECT sensor is a high-authority sensor at engine start-up and is used for open-loop control, as well as idle speed. Who is right?
Both technicians
The MAF sensor on a General Motors 3800 V-6 is being tested for contamination. Technician says that the sensor should show over 100 grams per second on a scan tool display when the accelerator is depressed to WOT (wide open throttle) on a running engine. Technician B says that the output frequency should exceed 7000 Hz when the accelerator pedal is depressed to WOT on a running engine. Who is right?
Both technicians
Two technicians are discussing a no-start (no spark) condition. Technician A says that an open CKP sensor could be the cause. Technician B says that a defective ignition control module (ICM) could be the cause. Which technician is correct?
Both technicians
Two technicians are discussing distributor ignition. Technician A says that the pickup coil in the distributor is used to pulse the ignition module (igniter). Technician B says that some distributor ignition systems use a Hall-effect system. Which technician is correct?
Both technicians
Two technicians are discussing testing MAP sensors. Technician A says that the MAP sensor voltage on a General Motors vehicle at idle should be about 1.0 volt. Technician B says that the MAP sensor voltage on a Chrysler vehicle at idle should be about 1.0 volt. Which technician is correct?
Both technicians
The "brain" of the computer is the ________.
CPU
Which computer component generates a steady stream of one-bit long voltage pulses?
Clock generator
The throttle body may be cleaned (if recommended by the vehicle manufacturer) if what conditions are occurring?
Coast-down stall Lower-than-normal idle speed Rough idle
When testing an ECT sensor on a vehicle, a digital multimeter can be used and the signal wires back probed. What setting should the technician use to test the sensor?
DC volts
All OBDII vehicles use what type of read-only memory?
EEPROM
A technician attaches one lead of a digital voltmeter to the ground terminal of the TP sensor and the other meter lead to the negative terminal of the battery. The ignition is turned on, engine off, and the meter displays 37.3 mV. Technician A says this is the signal voltage and is a little low. Technician B says the TP sensor ground circuit has excessive resistance. Who is right?
Neither technician
Two technicians are discussing Karman Vortex sensors. Technician A says that they contain a burn-off circuit to keep them clean. Technician B says that they contain a movable vane. Which technician is correct?
Neither technician
A technician is checking the operation of the electronic throttle control system by depressing the accelerator pedal when the gear selector is in PARK What is the most likely result if the system is functioning correctly?
No throttle movement
Technician A says that a MAF sensor is a high-authority sensor and is responsible for determining the fuel needs of the engine based on the measured amount of air entering the engine. Technician B says that a cold wire MAF sensor uses the electronics in the sensor itself to heat a wire 20°C below the temperature of the air entering the engine. Who is right?
Technician A only
Technician A says that a thorough visual inspection should be performed on all ignition components when diagnosing an engine performance problem Technician B says that platinum spark plugs can be re-gapped after use in an engine. Who is right?
Technician A only
Technician A says that other temperature sensors that operate like the ECT include transmission fluid temperature (TFT), and engine oil temperature sensors. Technician B says that all temperature sensors increase in resistance as the temperature decreases. Who is right?
Technician A only
Technician A says that pressure below atmospheric pressure is called vacuum and is measured in inches of mercury (Hg). Technician B says that a manifold absolute pressure (MAP) sensor uses a low vacuum in the sensor to determine the pressure. Who is right?
Technician A only
Technician A says that the 3 wires on the TP sensor include a 5-volt reference voltage from the PCM. Technician B says that a TP sensor is a three-wire variable resistor called a rheostat. Who is right?
Technician A only
Two technicians are diagnosing a poorly running engine. There are no diagnostic trouble codes. When the MAF sensor is unplugged, the engine runs better. Technician A says that this means the MAF is supplying incorrect air flow information to the PCM. Technician B says that this indicates the PCM is defective. Who is right?
Technician A only
When the ignition is first turned on a click noise is heard from under the hood of a vehicle equipped with ETC. Technician A says that this is the normal operation of the ETC self-test. Technician B says that the ETC motor should not move unless the engine is running. Which technician is correct?
Technician A only
A MAP sensor is being discussed. Technician A says that many MAP sensors act as a barometric pressure sensor when the ignition switch is turned off. Technician B says that on many MAP sensors the signal voltage should increase when the vacuum at the sensor decreases. Who is right?
Technician B only
A P0103 DTC is being discussed. Technician A says that a sensor circuit shorted-to-ground can be the cause. Technician B says that a defective MAF sensor could be the cause. Who is right?
Technician B only
Technician A says that temperature sensors decrease in resistance as the temperature increases; this is called positive temperature coefficient (PTC). Technician B says that some vehicle manufacturers use a stepped ECT circuit inside the PCM to broaden the accuracy of the sensor. Who is right?
Technician B only
Technician A says that the 3 wires on the TP sensor include a 5-volt reference voltage from PCM, plus the signal wire to PCM, and a ground wire to the engine block. Technician B says that the TP sensor is used by the PCM to determine torque converter engagement and transmission shift points. Who is right?
Technician B only
Technician A says that the TP sensor signal voltage should be about 0.5 volt at idle and increase to about 2.5 volts at wide-open throttle (WOT). Technician B says A TP sensor can be tested using a DMM, DSO, or scan tool. Who is right?
Technician B only
Two technicians are discussing a stepped ECT circuit. Technician A says that the sensor used for a stepped circuit is different from the one used in a non-stepped circuit. Technician B says that a stepped ECT circuit uses different internal resistance inside the PCM. Who is right?
Technician B only
Two technicians are discussing the IAT sensor. Technician A says that the IAT sensor is more important to the operation of the engine (higher authority) than the ECT sensor. Technician B says that the PCM adds fuel if the IAT indicates that the incoming air temperature is cold. Who is right?
Technician B only
After servicing the air filter on an ETC equipped vehicle, the technician has forgotten to connect the throttle motor wiring. What will happen when the vehicle is started?
The engine will start but not accelerate; idle speed between 1200 and 1600 RPM.
A compression-sensing ignition system is what type?
Waste-spark
When does the PCM perform a self test of the ETC system?
When the ignition switch is first rotated to the on position, before the engine starts
The MAF sensor is used mostly to determine the amount of ________ to deliver to the engine.
fuel
