Question 1

A typical EGR pintle-position sensor is what type of sensor?

Accepted Answer

A) Piezoelectric 
B) Wheatstone bridge 
C) Potentiometer 
D) Rheostat 
A) Piezoelectric 
B) Wheatstone bridge 
C) Potentiometer 
D) Rheostat C

Question 2

Blocking off the EGR valve passages will have no effect on the OBD-II system.

Accepted Answer

A) True 
 B)False  False

Question 3

Manually opening an EGR valve with a vacuum pump or scan tool will cause the engine to idle roughly or stall.

Accepted Answer

A) True 
 B)False  True

Question 4

Technician A says that a low-restriction exhaust system could prevent a back pressure-typeVacuum-controlled EGR valve from opening correctly. Technician B says restricted exhaust can cause the EGR valve position sensor to fail. Which technician is correct?

Accepted Answer

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

Question 5

A vehicle with a linear EGR valve has a piece of carbon stuck in the valve, causing it to be partially open all the time. What symptom would this cause?

Accepted Answer

A) Stalling 
B) High exhaust system pressure 
C) Both A and B 
D) Neither A nor B 
A) Stalling 
B) High exhaust system pressure 
C) Both A and B 
D) Neither A nor B

Question 6

A P0401 DTC (exhaust gas recirculation flow insufficient) is being discussed. Technician A says that a defective EGR valve could be the cause. Technician B says that clogged EGR passages could be the cause. Which technician is correct?

Accepted Answer

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

Question 7

In which of the following conditions is EGR not commanded?

Accepted Answer

A) Cold engine 
B) Wide open throttle 
C) Idle 
D) All of these are correct. 
A) Cold engine 
B) Wide open throttle 
C) Idle 
D) All of these are correct.

Question 8

When testing an EGR system for proper operation using a vacuum gauge, how much should intake manifold vacuum drop when the EGR valve is commanded open by a scan tool?

Accepted Answer

A) 6-8 PSI 
B) 6-8 in. Hg. 
C) 1-2 in. Hg. 
D) 14.7 PSI 
A) 6-8 PSI 
B) 6-8 in. Hg. 
C) 1-2 in. Hg. 
D) 14.7 PSI

Question 9

OBD-II regulations require that the EGR system be tested. Technician A says that the PCM can monitor the commanded position of the EGR valve to determine if it is functioning correctly. Technician B says that the PCM can open the EGR valve and monitor for a change in the MAP sensor or oxygen sensor reading to detect if the system is functioning correctly. Which technician is correct?

Accepted Answer

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

Question 10

The following statements are all correct EXCEPT ________.

Accepted Answer

A) Many vehicles use the MAP sensor to monitor EGR operation 
B) The MIL will be turned on after the second failure 
C) OBD-II vehicles require monitoring of the EGR system 
D) Linear EGR systems require exhaust backpressure 
A) Many vehicles use the MAP sensor to monitor EGR operation 
B) The MIL will be turned on after the second failure 
C) OBD-II vehicles require monitoring of the EGR system 
D) Linear EGR systems require exhaust backpressure

Question 11

The linear EGR valve uses ________ to control the opening of the valve.

Accepted Answer

A) Vacuum 
B) A pressure valve 
C) A pulse-width modulated solenoid 
D) None of these 
A) Vacuum 
B) A pressure valve 
C) A pulse-width modulated solenoid 
D) None of these

Question 12

EGR is used to control which exhaust emission?

Accepted Answer

A) Unburned hydrocarbons (H
C)  
B) Carbon monoxide (CO) 
C) Oxides of nitrogen (NOx) 
D) Carbon dioxide (CO2)  
A) Unburned hydrocarbons (H
C)  
B) Carbon monoxide (CO) 
C) Oxides of nitrogen (NOx) 
D) Carbon dioxide (CO2)

Question 13

Exhaust gas recirculation (EGR) is generally not needed under any of the following conditions EXCEPT ________.

Accepted Answer

A) Cold engine 
B) Idle speed 
C) Wide open throttle (WOT) 
D) Cruise speed 
A) Cold engine 
B) Idle speed 
C) Wide open throttle (WOT) 
D) Cruise speed

Question 14

Which of the following are symptoms of a clogged EGR passage?

Accepted Answer

A) Poor performance and lack of power. 
B) Detonation during acceleration or cruise 
C) Reduced NOx emissions 
D) Rough idle and stalling 
A) Poor performance and lack of power. 
B) Detonation during acceleration or cruise 
C) Reduced NOx emissions 
D) Rough idle and stalling

Question 15

What causes the nitrogen and oxygen in the air to combine and form NOx?

Accepted Answer

A) Heat above 2,500 F (1,370 
C)  
B) Any spark will cause this to occur 
C) Chemical reaction in the catalytic converter 
D) Sunlight 
A) Heat above 2,500 F (1,370 
C)  
B) Any spark will cause this to occur 
C) Chemical reaction in the catalytic converter 
D) Sunlight

Exam 84: Exhaust Gas Recirculation Systems

A typical EGR pintle-position sensor is what type of sensor?

Blocking off the EGR valve passages will have no effect on the OBD-II system.

Manually opening an EGR valve with a vacuum pump or scan tool will cause the engine to idle roughly or stall.

Technician A says that a low-restriction exhaust system could prevent a back pressure-typeVacuum-controlled EGR valve from opening correctly. Technician B says restricted exhaust can cause the EGR valve position sensor to fail. Which technician is correct?

A vehicle with a linear EGR valve has a piece of carbon stuck in the valve, causing it to be partially open all the time. What symptom would this cause?

A P0401 DTC (exhaust gas recirculation flow insufficient) is being discussed. Technician A says that a defective EGR valve could be the cause. Technician B says that clogged EGR passages could be the cause. Which technician is correct?

In which of the following conditions is EGR not commanded?

When testing an EGR system for proper operation using a vacuum gauge, how much should intake manifold vacuum drop when the EGR valve is commanded open by a scan tool?

The following statements are all correct EXCEPT ________.

The linear EGR valve uses ________ to control the opening of the valve.

EGR is used to control which exhaust emission?

Exhaust gas recirculation (EGR) is generally not needed under any of the following conditions EXCEPT ________.

Which of the following are symptoms of a clogged EGR passage?

What causes the nitrogen and oxygen in the air to combine and form NOx?

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