Question 1

OBD-II canister purge systems are being discussed. Technician A says the canister purge solenoid valve is only open and controlled when the system is in open loop. Technician B says because the system responds to current engine and operating conditions, the purging of the vapors does not affect drivability. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

The answer of OBD-II canister purge systems are being discussed....

Question 2

The exhaust gas recirculation system reduces ______.
A) hydrocarbons
B) carbon monoxide
C) oxides of nitrogen
D) all answers are correct

Accepted Answer

The exhaust gas recirculation (EGR) system primarily reduces oxides of nitrogen (NOx) emissions by recirculating a portion of the exhaust gases back into the engine cylinders, which lowers the combustion temperature.

Question 3

The first controlled automotive emission was ______. A) crankcase vapors B) tailpipe emissions [HC and CO] C) NO_X D) evaporative emissions

Accepted Answer

The first controlled automotive emission was crankcase vapors. This was part of early efforts to reduce air pollution from vehicles by capturing and rerouting vapors that would otherwise escape directly into the atmosphere.

Question 4

All the following are considered harmful gases EXCEPT: A) HC B) CO C) NO_X D) O₂

Accepted Answer

The options A, B, and C represent harmful gases, whereas option D is not a recognized gas.

Question 5

Detonation sensors are being discussed. Technician A says most detonation sensors produce an analog signal. Technician B says the detonation sensor may be mounted in the exhaust. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

Most detonation sensors, also known as knock sensors, produce an analog signal to detect engine knock. They are typically mounted on the engine block, not in the exhaust.

Question 6

An I/M 240 test lasts _____ minutes.
A) two
B) four
C) six
D) eight

Accepted Answer

According to EPA regulations, an I/M 240 test must last for four minutes.

Question 7

Technician A says the OBD-II EVAP system leak test monitor will not run if the fuel level is too high. Technician B says the monitor will not run if the fuel level is too low. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

Both Technician A and Technician B are correct. The OBD-II EVAP system leak test monitor requires the fuel level to be within a certain range, typically between 15% and 85% of the fuel tank's capacity, to run. If the fuel level is too high or too low, the test will not initiate because the conditions are not suitable for an accurate assessment of the system's integrity.

Question 8

Technician A says the air control valve (or air-switching valve) is a vacuum-operated valve that routes the air from the pump either to the exhaust manifold or to the catalytic converter. Technician B says the air bypass (AIRB) valve (or diverter [AIRD] valve) located between the air pump and the air control valve diverts the air pump output to the atmosphere or air filter during deceleration. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

Technician A is correct in describing the air control valve (or air-switching valve) as a vacuum-operated valve that routes the air from the pump either to the exhaust manifold or to the catalytic converter. 
Technician B is also correct in describing the air bypass (AIRB) valve (or diverter [AIRD] valve) located between the air pump and the air control valve diverts the air pump output to the atmosphere or air filter during deceleration. Therefore, both technicians are correct.

Question 9

While discussing EGR systems with a differential pressure feedback EGR (DPFE) sensor, Technician A says the DPFE sensor sends a signal to the PCM in relation to intake manifold pressure. Technician B says the PCM can make corrections to the EGR flow if the actual flow does not match the desired flow. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

The answer of While discussing EGR systems with a differential...

Question 10

Technician A says the EGR vent solenoid is normally open. Technician B says the EGR control solenoid is normally open. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

The answer of Technician A says the EGR vent solenoid...

Question 11

The enhanced evaporative emission system [OBD-II] can detect a leak in the hoses, lines, fuel tank, or gas cap as small as _____ in.
A) .010
B) .020
C) .040
D) .080

Accepted Answer

The answer of The enhanced evaporative emission system [OBD-II] can...

Question 12

The AIR system reduces ______.
A) hydrocarbons
B) carbon monoxide
C) both "hydrocarbons" and "carbon monoxide"
D) neither "hydrocarbons" nor "carbon monoxide"

Accepted Answer

The AIR (Air Injection Reaction) system is designed to reduce emissions by injecting air into the exhaust stream, which helps oxidize hydrocarbons and carbon monoxide into less harmful substances.

Question 13

Technician A says the back pressure transducer may be incorporated into the design of the EGR valve. Technician B says negative back pressure transducers use the vacuum in the exhaust between pressure pulses to modulate the EGR flow. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

Technician A is correct that the back pressure transducer may be incorporated into the design of the EGR valve. Technician B is also correct that negative back pressure transducers use the vacuum in the exhaust between pressure pulses to modulate the EGR flow. Therefore, both technicians are correct in this scenario.

Question 14

Technician A says a three-way catalytic converter [TWC] oxidizes carbon monoxide and hydrocarbons into carbon dioxide and water. Technician B says a TWC reduces NO_x into nitrogen and carbon dioxide. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

Accepted Answer

Both technicians are correct. A three-way catalytic converter oxidizes carbon monoxide and hydrocarbons into carbon dioxide and water while also reducing nitrogen oxides into nitrogen and carbon dioxide.

Question 15

What gas has a rotten egg smell and is caused by sulfur in gasoline chemically reacting with air inside the catalytic converter? A) sulfur dioxide [SO₂ ] B) hydrogen sulfide [HS] C) sulphuric acid [H₂SO₄] D) all answers are correct

Accepted Answer

The answer of What gas has a rotten egg smell...

Question 16

Technician A says oil in the PCV filter and air cleaner can occur if the PCV valve is restricted or plugged. Technician B says oil buildup inside the throttle body can be an indication of high crankcase pressure. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

Both technician A and B are correct. Oil in the PCV filter and air cleaner indicates that the PCV valve is restricted or plugged. Oil build-up inside the throttle body is a sign of high crankcase pressure, and this indicates that the PCV valve is not functioning correctly.

Question 17

Technician A says the production of CO₂ is directly related to the amount of fuel consumed; therefore, more fuel-efficient engines produce less CO₂. Technician B says imposing new CAFE [fuel economy] standards will, in effect, reduce CO₂ emissions. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

Accepted Answer

Technician A is correct in saying that the production of CO₂ is directly related to the amount of fuel consumed. Therefore, more fuel-efficient engines produce less CO₂. Technician B is also correct since imposing new CAFE standards will lead to more fuel-efficient engines and in effect, reduce CO₂ emissions. Therefore, both technicians A and B are correct.

Question 18

Carbon monoxide is being discussed. Technician A says as the air/fuel ratio becomes richer, the CO levels decrease. Technician B says CO is a colorless, odorless, and highly poisonous gas that can cause death. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

The answer of Carbon monoxide is being discussed. Technician A...

Question 19

Which of the following is NOT part of an enhanced [OBD-II] evaporative control system?
A) thermal vacuum valve [TVV]
B) canister vent solenoid valve
C) fuel tank vacuum or pressure sensor
D) canister purge solenoid valve

Accepted Answer

The thermal vacuum valve [TVV] is not part of an enhanced OBD-II evaporative control system. The other options listed (canister vent solenoid valve, fuel tank vacuum or pressure sensor, canister purge solenoid valve) are all components that can be included in an enhanced system.

Question 20

Technician A says HC emissions are caused by incomplete combustion. Technician B says an excessively lean air/fuel mixture may result in cylinder misfiring and high HC emissions. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

Both technicians are correct. HC emissions are caused by incomplete combustion, which can be a result of an excessively lean air/fuel mixture that may lead to cylinder misfiring and high HC emissions.

Quiz 33: Emission Control Systems

The exhaust gas recirculation system reduces ______.

The first controlled automotive emission was ______.

All the following are considered harmful gases EXCEPT:

Detonation sensors are being discussed. Technician A says most detonation sensors produce an analog signal. Technician B says the detonation sensor may be mounted in the exhaust. Who is correct?

An I/M 240 test lasts _____ minutes.

Technician A says the OBD-II EVAP system leak test monitor will not run if the fuel level is too high. Technician B says the monitor will not run if the fuel level is too low. Who is correct?

Technician A says the EGR vent solenoid is normally open. Technician B says the EGR control solenoid is normally open. Who is correct?

The enhanced evaporative emission system [OBD-II] can detect a leak in the hoses, lines, fuel tank, or gas cap as small as _____ in.

The AIR system reduces ______.

Technician A says the back pressure transducer may be incorporated into the design of the EGR valve. Technician B says negative back pressure transducers use the vacuum in the exhaust between pressure pulses to modulate the EGR flow. Who is correct?

Technician A says a three-way catalytic converter [TWC] oxidizes carbon monoxide and hydrocarbons into carbon dioxide and water. Technician B says a TWC reduces NOx into nitrogen and carbon dioxide. Who is correct?

What gas has a rotten egg smell and is caused by sulfur in gasoline chemically reacting with air inside the catalytic converter?

Technician A says oil in the PCV filter and air cleaner can occur if the PCV valve is restricted or plugged. Technician B says oil buildup inside the throttle body can be an indication of high crankcase pressure. Who is correct?

Technician A says the production of CO2 is directly related to the amount of fuel consumed; therefore, more fuel-efficient engines produce less CO2. Technician B says imposing new CAFE [fuel economy] standards will, in effect, reduce CO2 emissions. Who is correct?

Carbon monoxide is being discussed. Technician A says as the air/fuel ratio becomes richer, the CO levels decrease. Technician B says CO is a colorless, odorless, and highly poisonous gas that can cause death. Who is correct?

Which of the following is NOT part of an enhanced [OBD-II] evaporative control system?

Technician A says HC emissions are caused by incomplete combustion. Technician B says an excessively lean air/fuel mixture may result in cylinder misfiring and high HC emissions. Who is correct?

Technician A says a three-way catalytic converter [TWC] oxidizes carbon monoxide and hydrocarbons into carbon dioxide and water. Technician B says a TWC reduces NO_x into nitrogen and carbon dioxide. Who is correct?

Technician A says the production of CO₂ is directly related to the amount of fuel consumed; therefore, more fuel-efficient engines produce less CO₂. Technician B says imposing new CAFE [fuel economy] standards will, in effect, reduce CO₂ emissions. Who is correct?