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AEP > hw 10 > Flashcards

hw 10 Flashcards

1
Q

Surging at low speeds or a rough idle may occur if the EGR valve is stuck closed.

A

False

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2
Q

Enable criteria are the conditions that have to be met in order for the PCM to run a specific test of a system.

A

True

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3
Q

The OBD II AIR system is meant only to operate long enough to warm the exhaust and help promote catalytic converter light-off by burning left-over HC and CO in the exhaust manifold of a cold engine.

A

True

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4
Q

Cylinders having excessive blow by may cause oil to be present in the air cleaner.

A

True’

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5
Q

High oxygen levels are a good indicator of a rich air-fuel ratio.

A

False

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6
Q

Misfiring of the ignition system may result in high hydrocarbon readings.

A

‘True’.

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7
Q

If gasoline is allowed to evaporate into the air it becomes a significant source of hydrocarbon emissions.

A

True’.

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8
Q

In a 2001 or newer OBD II system the PCM will set a code if the evaporative system has a leak as small as .020” in size.

A

True’.

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9
Q

Technician A says oil accumulation in the air cleaner may indicate the PCV valve or hose is restricted. Technician B says a restricted PCV valve or hose may result in the accumulation of moisture and sludge in the engine and engine oil. Who is correct?

A

Both A and B

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10
Q

In the PCV system, crankcase vapors are recycled to the:

A

Intake manifold

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11
Q

Which exhaust gas /gasses are controlled by the EGR valve?

A

NOx

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12
Q

The catalytic converter may be tested with the

a.

Delta temperature test
b.

O2 storage test
c.

Delta pressure feedback test
d.

Both A and B

A

Both A and B

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13
Q

Excessive CO emissions may be caused by:

A

Rich air-fuel mixtures

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14
Q

The OBD II AIR system pumps air into the;

A

Exhaust manifold

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15
Q

The vent valve in an evaporative emissions system may be:
a.

Opened to allow fresh air through the charcoal canister
b.

Closed with the purge valve open while the PCM monitors the fuel tank pressure sensor for vacuum
c.

Closed to prevent the system from purging
d.

Both A and B

A

Both A and B

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16
Q

Oxides of nitrogen (NOx) are formed when combustion temperatures reach more than:

A

2,500 degrees

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17
Q

Excessive HC emissions may be caused by:

A

Ignition system defects
Vacuum leaks
Excessively lean or rich air-fuel ratio
All of the above

18
Q

Which exhaust gas is near its highest level when the air/fuel ratio is near stoichiometric?

A

CO2

19
Q

A three-way catalyst is named for its ability to reduce which emissions:

A

NOx, CO, and HC

20
Q

Fresh air is allowed to enter the charcoal canister:

A

When the PCM purges the canister

21
Q

Technician A says each module in a CAN system receives every communication on the serial data bus. Technician B says only the messages with the correct heading are responded to by a module in a CAN system. Who is correct?

A

Both A and B

22
Q

Bi-directional control means the:

A

Technician can tell a computer to exercise an output

23
Q

Technician A says an open in star network bus will affect all the modules on the network. Technician B says an open in a loop network will isolate a module from the network. Who is correct?

A

Neither A nor B

24
Q

The components of the PCM responsible for controlling circuits or devices are called:

A

Drivers

25
Q

All of the following are PCM actuators except:

A

PCV valve

26
Q

All of the following are the same communication protocol except:

A

ISO 9141

27
Q

What is the term used to define the operating conditions that must be present during a second trip to set a code?

A

Similar conditions

28
Q

A flashing MIL indicates a

A

Misfire that may damage the catalytic converter

29
Q

Technician A says PCMs in an OBD II system may have replaceable PROMs. Technician B says a new PCM will need to be flashed before it can be used in a vehicle. Who is correct?

A

Technician B only

30
Q

Technician A says long term fuel trim works to bring short term fuel trim close to zero percent correction. Technician B says if a lean condition exists because of a vacuum leak, the long term fuel trim will have a plus (+) number on the scan tool. Who is correct?

A

Both A and B

31
Q

The output voltage of a downstream O2 sensor is fluctuating when the engine is at operating temperature. Technician A says the catalytic converter is working efficiently. Technician B says the O2 sensor may need to be replaced. Who is correct?

A

Neither A nor B

32
Q

The MIL light of an OBD-equipped vehicle is flashing. Technician A says a spark plug wire may be shorted to ground. Technician B says a cylinder may have low compression. Who is correct?

A

Both A and B

33
Q

Technician A says enabling criteria defines the criteria that must be met before the vehicle will enter closed loop. Technician B says enabling criteria defines the criteria that must be met in order for a monitor test to be completed. Who is correct?

A

Both A and B

34
Q

The signal that alerts the misfire monitor that a misfire may be occurring is provided by the:

A

Crankshaft position sensor

35
Q

The PCM has the option of turning the MIL off when the diagnostic test which caused the MIL to light passes for:

A

Three consecutive trips

36
Q

Technician A says a type “A” misfire will set a trouble code on the first failure. Technician B says a type “B” misfire will set a trouble code on the first failure. Who is correct?

A

Technician A only

37
Q

Which of the following OBD-II test modes allows scan tools to access freeze frame data?

A

Mode 2

38
Q

Technician A says the basic advantage of the snapshot feature on a scan tool is the ability to look at the existing conditions (a single frame of data) when a code was set. Technician B says GM failure records do the same thing as a snapshot but also include any fault stored in memory, not just those related to the emissions-related circuits. Who is correct?

A

Neither A nor B

39
Q

The AIR pump is normally used:

A

On startup

40
Q

Technician A says an OBD II trip is the same as a drive cycle. Technician B says a trip is a period of operation that allows a monitor to complete. Who is correct?

A

Technician B only

AEP (5 decks)

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