Deck 12: General Motors Computerized Engine Controls

Question 1

Pressure sensors are being discussed. Technician A says GM fuel injected vehicles use separate sensors to measure engine load and barometric pressure. Technician B says the MAP sensor operates on a 5 volt reference. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Answer 1

B

Question 2

On a GM vehicle, in order to properly control the air-fuel ratio during cranking mode the ECM relies primarily on information from which sensors?

A) O₂S and TPS
B) MAP/MAF sensor and TPS
C) ECT sensor and TPS
D) IAT sensor and TPS

Answer 2

C

Question 3

GM engines include a feature, called the engine metal overtemp mode , whereby at temperatures above _____ the ECM will selectively disable half of the cylinders at a time on a V6 or V8 engine to keep the engine temperature from reaching destructive levels.

A) 70ºF
B) 170ºF
C) 270ºF
D) 370ºF

Answer 3

C

Question 4

A GM vehicle with high idle speed is being diagnosed. Technician A says if the IAC counts show a value of 0, a vacuum leak is a possible cause. Technician B says if the IAC counts show a value of 0, the ECM may not be able to control the IAC. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 5

The EONV (engine off natural vacuum) test is being discussed. Technician A says that to perform it, the ECM is kept powered for up to 4 minutes after the ignition switch is turned off. Technician B says that the natural vacuum created in the fuel tank as the engine cools, is from about 3 inches to about 5 inches of water.  Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 6

MAF sensors are being discussed. Technician A says to use a DC voltmeter to measure the sensor's output. Technician B says to use a Hertz meter to measure the sensor's output. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 7

Ordinary engine noise, known as background noise, can be used to allow the ECM to detect some circuit faults. The sensor used to detect the engine noise is the:

A) TPS
B) KS
C) MAP sensor
D) ECT sensor

Question 8

The system that allows GM to retrieve vehicle diagnostic reports via satellite is called:

A) OnStar
B) Cadillac User Experience (CUE)
C) GM navigational system
D) GM Multiplexing

Question 9

The ECM may turn the A/C clutch on or off in all of the following situations EXCEPT :

A) during WOT operation
B) if power steering pressure exceeds a specified value during idle
C) when the electric cooling fan is turned on
D) when the A/C control switch is turned on

Question 10

In modern GM engines, what type of sensor is the throttle position sensor (TPS)?

A) Thermistor
B) Hall effect sensors
C) Rheostat
D) Potentiometer

Question 11

The idle air control (IAC) assembly on a GM fuel-injected vehicle is a(n) _____ and pintle valve assembly.

A) stepper motor
B) stepper solenoid
C) AC motor
D) permanent magnet motor

Question 12

The body control module (BCM) is being discussed. Technician A says it is a microcomputer with about the same computer power as the ECM. Technician B says it is a microcomputer that exchanges information with the ECM. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 13

Distributors are no longer needed because of many advances in technology. What is NOT one of these?

A) Spark advance can be controlled by a computer.
B) Tach reference signals can be taken directly from the crankshaft.
C) Camshaft position sensors can control simple vacuum advance spark systems.
D) Spark timing can be made permanently fixed.

Question 14

The assembly line  data link connector (ALDL) on a non-OBDII vehicle has _______ terminals.

A) sixteen
B) fourteen
C) twelve
D) ten

Question 15

Which statement about the engine coolant temperature sensor is true?

A) Its resistance decreases as the temperature increases
B) Its resistance increases as the temperature increases
C) It is a PTC thermistor
D) Both A and C are correct

Question 16

Many GM systems place an ECM-generated signal, known as a bias voltage , on the oxygen sensor signal until it begins to generate its own voltage. The value of this bias voltage is:

A) 45 mV
B) 450 mV
C) 4.5 V
D) 5 V

Question 17

TPS adjustment is being discussed. Technician A says all PFI systems are adjustable. Technician B says that performing a correction of the minimum idle speed adjustment is cause to perform a TPS adjustment. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 18

In order to make accurate measurements of reference voltages, the voltmeter must have an input impedance of at least:

A) 100 Ω
B) 1 MΩ
C) 10 MΩ
D) 100 MΩ

Question 19

Which level of tach reference information identifies for the ECM which cylinder is on the compression stroke?

A) Level four
B) Level three
C) Level two
D) Level one

Question 20

Technician A says a Central Multiport Fuel Injection (CMFI) system pulses all injectors simultaneously. Technician B says a sequential fuel injection (SFI) system pulses each injector individually. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B