A8 ENGINE PERFORMANCE PRACTICE TEST
QUESTIONS WITH 100% SOLVED
ANSWERS.
1 of 46
Definition
A vacuum gauge indicates low vacuum (12 inches of mercury). Technician
A says late valve timing will cause a low vacuum reading. Technician B says
to connect the gauge to a venturi vacuum port.
Who is correct?
Tech A
Tech B
Both technicians
Neither technician
Give this one a try later!
, C. Both. The TPS is a 5-volt sensor. Three wires are used on most TPSs include a
5-volt reference, a signal, a ground. If the signal wire is back-probed with the
key on, then the voltage reading should be around 1.0 volt or less at idle and
around
4.5 volts at wide-open throttle.
A. The fan is used to circulate air through the radiator at a stop or when idling
and temperatures are high. A defective fan could cause the overheating
complaint.
If the thermostat was opening too soon, then the vehicle would take a long time
to reach operating temperature, if it reached it at all.
A. The purpose of the secondary air system is to inject additional air into the
catalytic converter to help the converter oxidize the HC and CO emissions.
The secondary air system is never used to lean out the air/ fuel mixture.
A. Late valve timing will cause the valves to open and close at the wrong
time in relation to piston position. This will cause a low vacuum reading.
The vacuum gauge should be connected to manifold vacuum, not
venturi vacuum.
Don't know?
2 of 46
Definition
Technician A that one of the first steps in diagnosing any EGR valve
related concern is to check the vacuum and electrical connections.
Technician B says that in many systems, the PCM uses other sensor
inputs that could cause an EGR problem, and therefore DTCs should
be corrected before replacing any EGR components. Who is
correct?
A. Tech A
, B. Tech B
C. Both technicians
D.Neither technician
Give this one a try later!
C. Both. Some PCMs require the programmable read only memory (PROM) chip
to be transferred from the old PCM when replacing. Some PCMs use an
electronically erasable programmable read-only memory (EEPROM) chip that
requires the PCM be flash programmed when replaced.
C. Both. A good visual inspection is part of any diagnostic routine and
should be performed after the complaint is verified. The PCM uses many
sensors to determine the amount of EGR flow to allow; thus, diagnostic
trouble codes should be corrected before replacing any EGR components.
C. Both. A good oxygen sensor should rapidly switch from 100 to 900 millivolts.
This can be tested with a DMM set on the 2-volt scale or with an oscilloscope.
C. Both. If an OBD II vehicle is equipped with a secondary air-injection
system, then the PCM must run monitors on it to verify correct operation.
Many OBD I
vehicles were equipped with secondary air; however, the PCM could not monitor
the system.
Don't know?
3 of 46
Definition
Technician A says the PCM will increase the fuel injector pulse width
if there is no oxygen in the exhaust. Technician B says if there is a
lean condition, then the short-term fuel trim (STF) will show a minus
, value on the scan tool. Who is correct?
A. Tech A
B. Tech B
C. Both technicians
D.Neither technician
Give this one a try later!
C. Both. If an OBD II vehicle is equipped with a secondary air-injection
system, then the PCM must run monitors on it to verify correct operation.
Many OBD I
vehicles were equipped with secondary air; however, the PCM could not monitor
the system.
A. The purpose of the secondary air system is to inject additional air into the
catalytic converter to help the converter oxidize the HC and CO emissions.
The secondary air system is never used to lean out the air/ fuel mixture.
C. Both. Aeration is the formation of air bubbles. Overfilling the crankcase with
oil can cause this aeration, and the air bubbles can lead to lifter noise. Another
cause of lifter noise is the use of engine oil that is too thin or the viscosity too
low.
D. If there is no oxygen in the exhaust, then this indicates a rich condition.
The PCM will decrease fuel injector pulse width, not increase it.
If there is a lean condition, then STF will show a plus sign indicating it is
adding fuel.
The PCM increases or decreases the fuel injector pulse width to control the
air/ fuel mixture based on what the oxygen sensor signal sends.
Don't know?
4 of 46
QUESTIONS WITH 100% SOLVED
ANSWERS.
1 of 46
Definition
A vacuum gauge indicates low vacuum (12 inches of mercury). Technician
A says late valve timing will cause a low vacuum reading. Technician B says
to connect the gauge to a venturi vacuum port.
Who is correct?
Tech A
Tech B
Both technicians
Neither technician
Give this one a try later!
, C. Both. The TPS is a 5-volt sensor. Three wires are used on most TPSs include a
5-volt reference, a signal, a ground. If the signal wire is back-probed with the
key on, then the voltage reading should be around 1.0 volt or less at idle and
around
4.5 volts at wide-open throttle.
A. The fan is used to circulate air through the radiator at a stop or when idling
and temperatures are high. A defective fan could cause the overheating
complaint.
If the thermostat was opening too soon, then the vehicle would take a long time
to reach operating temperature, if it reached it at all.
A. The purpose of the secondary air system is to inject additional air into the
catalytic converter to help the converter oxidize the HC and CO emissions.
The secondary air system is never used to lean out the air/ fuel mixture.
A. Late valve timing will cause the valves to open and close at the wrong
time in relation to piston position. This will cause a low vacuum reading.
The vacuum gauge should be connected to manifold vacuum, not
venturi vacuum.
Don't know?
2 of 46
Definition
Technician A that one of the first steps in diagnosing any EGR valve
related concern is to check the vacuum and electrical connections.
Technician B says that in many systems, the PCM uses other sensor
inputs that could cause an EGR problem, and therefore DTCs should
be corrected before replacing any EGR components. Who is
correct?
A. Tech A
, B. Tech B
C. Both technicians
D.Neither technician
Give this one a try later!
C. Both. Some PCMs require the programmable read only memory (PROM) chip
to be transferred from the old PCM when replacing. Some PCMs use an
electronically erasable programmable read-only memory (EEPROM) chip that
requires the PCM be flash programmed when replaced.
C. Both. A good visual inspection is part of any diagnostic routine and
should be performed after the complaint is verified. The PCM uses many
sensors to determine the amount of EGR flow to allow; thus, diagnostic
trouble codes should be corrected before replacing any EGR components.
C. Both. A good oxygen sensor should rapidly switch from 100 to 900 millivolts.
This can be tested with a DMM set on the 2-volt scale or with an oscilloscope.
C. Both. If an OBD II vehicle is equipped with a secondary air-injection
system, then the PCM must run monitors on it to verify correct operation.
Many OBD I
vehicles were equipped with secondary air; however, the PCM could not monitor
the system.
Don't know?
3 of 46
Definition
Technician A says the PCM will increase the fuel injector pulse width
if there is no oxygen in the exhaust. Technician B says if there is a
lean condition, then the short-term fuel trim (STF) will show a minus
, value on the scan tool. Who is correct?
A. Tech A
B. Tech B
C. Both technicians
D.Neither technician
Give this one a try later!
C. Both. If an OBD II vehicle is equipped with a secondary air-injection
system, then the PCM must run monitors on it to verify correct operation.
Many OBD I
vehicles were equipped with secondary air; however, the PCM could not monitor
the system.
A. The purpose of the secondary air system is to inject additional air into the
catalytic converter to help the converter oxidize the HC and CO emissions.
The secondary air system is never used to lean out the air/ fuel mixture.
C. Both. Aeration is the formation of air bubbles. Overfilling the crankcase with
oil can cause this aeration, and the air bubbles can lead to lifter noise. Another
cause of lifter noise is the use of engine oil that is too thin or the viscosity too
low.
D. If there is no oxygen in the exhaust, then this indicates a rich condition.
The PCM will decrease fuel injector pulse width, not increase it.
If there is a lean condition, then STF will show a plus sign indicating it is
adding fuel.
The PCM increases or decreases the fuel injector pulse width to control the
air/ fuel mixture based on what the oxygen sensor signal sends.
Don't know?
4 of 46
