Question 1

The O2S [oxygen] sensor should toggle between rich and lean ____________________ to ____________________ times in a ten-second period?

Accepted Answer

10 to 40
ten to forty

Question 2

Describe a speed density system.

Accepted Answer

A speed density system relies heavily on the MAP sensor for fuel calculation.

Question 3

A rich air/fuel mixture is being discussed. Technician A says oxygen content in the exhaust will be high. Technician B says the O2 sensor voltage will be high. Who is correct?

Accepted Answer

A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B 
A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B B

Question 4

Which of the following sensors is used to modify the engine's air/fuel mixture based on oxygen in the exhaust?

Accepted Answer

A)  O2 sensor 
B)  TP sensor 
C)  MAP sensor 
D)  MAF sensor 
A)  O2 sensor 
B)  TP sensor 
C)  MAP sensor 
D)  MAF sensor

Question 5

How can a hot wire-type mass airflow sensor [MAF] be cleaned?

Accepted Answer

By gently wiping it

Question 6

Technician A says throttle body cleaner may be used to clean the IAC motor internal components. Technician B says on some vehicles, IAC motor damage can occur if the pintle is cleaned with throttle body cleaner. Who is correct?

Accepted Answer

A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B 
A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B

Question 7

Technician A says an intake manifold vacuum leak may cause a high idle speed. Technician B says a dirty IAC bypass passage will not cause the idle speed to be below specifications. Who is correct?

Accepted Answer

A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B 
A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B

Question 8

Injector cleaning is being discussed. Technician A uses a wire brush to clean the tips of the injectors. Technician B soaks the injector in cleaning solvent. Who is correct?

Accepted Answer

A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B 
A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B

Question 9

It is impossible to visually check the spray pattern and volume of port system injectors.

Accepted Answer

A) True 
 B)False

Question 10

A technician is testing a fuel injection system with a scan tool. While the engine is running in closed loop, he loosens a vacuum hose to create a small vacuum leak. Initially the STFT rises and the LTFT remains unchanged. After a few minutes the STFT returns to near zero and the LTFT rises. This test proves that ______.

Accepted Answer

A)  the system is running rich 
B)  the system is running lean 
C)  the O2S sensor is faulty 
D)  the system is working normally 
A)  the system is running rich 
B)  the system is running lean 
C)  the O2S sensor is faulty 
D)  the system is working normally

Question 11

Technician A says higher than normal idle speed may be caused by an air-conditioning switch that is always closed. Technician B says higher than normal idle speed may be caused by a defective engine coolant temperature sensor. Who is correct?

Accepted Answer

A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B 
A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B

Question 12

____________________ and hold injector circuits use two driver circuits to control injector action.

Accepted Answer

The answer of ____________________ and hold injector circuits use two...

Question 13

One test of a GM hot film mass airflow meter includes tapping it with a plastic mallet or screwdriver handle.

Accepted Answer

A) True 
 B)False

Question 14

Most heated oxygen sensors have _____ wire(s) connected to them.

Accepted Answer

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

Question 15

Creating a large vacuum leak will cause the short-term fuel trim (STFT) and long-term fuel trim (LTFT) to decrease.

Accepted Answer

A) True 
 B)False

Question 16

A vehicle with excessively high fuel pressure is being diagnosed. Technician A says the problem could be a restricted fuel return line. Technician B says the problem could be a shorted [closed] fuel pump relay. Who is correct?

Accepted Answer

A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B 
A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B

Question 17

Preliminary checks are being discussed. Technician A says to run specific fuel injection tests first. Technician B says most driveability concerns are caused by PCM-related problems. Who is correct?

Accepted Answer

A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B 
A)  A only 
B)  B only 
C)  both A and B 
D)  neither A nor B

Question 18

Vacuum leaks in speed density systems can be verified by watching the _____ on a scan tool.

Accepted Answer

A)  O2S sensor crosscounts 
B)  IAC counts 
C)  mass airflow [MAF] voltage 
D)  delta EGR [exhaust gas recirculation] 
A)  O2S sensor crosscounts 
B)  IAC counts 
C)  mass airflow [MAF] voltage 
D)  delta EGR [exhaust gas recirculation]

Question 19

An APP [accelerator pedal position] sensor is found on vehicles with ______.

Accepted Answer

A)  automatic transmissions 
B)  automatic traction control 
C)  throttle by wire 
D)  GDI [gasoline direct injection] 
A)  automatic transmissions 
B)  automatic traction control 
C)  throttle by wire 
D)  GDI [gasoline direct injection]

Question 20

If the IAC pintle is extended too far, the motor can be damaged during installation.

Accepted Answer

A) True 
 B)False

Exam 31: Fuel Injection System Diagnosis and Service

The O2S [oxygen] sensor should toggle between rich and lean ____________________ to ____________________ times in a ten-second period?

Describe a speed density system.

A rich air/fuel mixture is being discussed. Technician A says oxygen content in the exhaust will be high. Technician B says the O2 sensor voltage will be high. Who is correct?

Which of the following sensors is used to modify the engine's air/fuel mixture based on oxygen in the exhaust?

How can a hot wire-type mass airflow sensor [MAF] be cleaned?

Technician A says throttle body cleaner may be used to clean the IAC motor internal components. Technician B says on some vehicles, IAC motor damage can occur if the pintle is cleaned with throttle body cleaner. Who is correct?

Technician A says an intake manifold vacuum leak may cause a high idle speed. Technician B says a dirty IAC bypass passage will not cause the idle speed to be below specifications. Who is correct?

Injector cleaning is being discussed. Technician A uses a wire brush to clean the tips of the injectors. Technician B soaks the injector in cleaning solvent. Who is correct?

It is impossible to visually check the spray pattern and volume of port system injectors.

Technician A says higher than normal idle speed may be caused by an air-conditioning switch that is always closed. Technician B says higher than normal idle speed may be caused by a defective engine coolant temperature sensor. Who is correct?

____________________ and hold injector circuits use two driver circuits to control injector action.

One test of a GM hot film mass airflow meter includes tapping it with a plastic mallet or screwdriver handle.

Most heated oxygen sensors have _____ wire(s) connected to them.

Creating a large vacuum leak will cause the short-term fuel trim (STFT) and long-term fuel trim (LTFT) to decrease.

A vehicle with excessively high fuel pressure is being diagnosed. Technician A says the problem could be a restricted fuel return line. Technician B says the problem could be a shorted [closed] fuel pump relay. Who is correct?

Preliminary checks are being discussed. Technician A says to run specific fuel injection tests first. Technician B says most driveability concerns are caused by PCM-related problems. Who is correct?

Vacuum leaks in speed density systems can be verified by watching the _____ on a scan tool.

An APP [accelerator pedal position] sensor is found on vehicles with ______.

If the IAC pintle is extended too far, the motor can be damaged during installation.

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The O₂S [oxygen] sensor should toggle between rich and lean to times in a ten-second period?

A rich air/fuel mixture is being discussed. Technician A says oxygen content in the exhaust will be high. Technician B says the O₂ sensor voltage will be high. Who is correct?