Question 1

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?

Accepted Answer

The DPFE sensor measures the pressure difference across the EGR valve to determine EGR flow, not intake manifold pressure. The PCM uses this information to adjust EGR flow to match the desired levels.

Question 2

The first controlled automotive emission was ______.

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 3

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?

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 4

Technician A says the EVAP monitor for an OBD-II system determines whether there is sufficient purge flow by varying the purge solenoid duty cycle while monitoring change in STFT. Technician B says the canister vent solenoid must be open during the EVAP pressure test portion of the monitor. Who is correct?

Accepted Answer

Technician A is correct because the EVAP monitor checks for sufficient purge flow by varying the purge solenoid duty cycle and observing changes in the Short Term Fuel Trim (STFT). Technician B is incorrect because the canister vent solenoid should be closed during the EVAP pressure test to seal the system and check for leaks.

Question 5

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

Accepted Answer

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

Question 6

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?

Accepted Answer

Both Technician A and Technician B are correct. Technician A correctly describes the function of the air control valve, which is indeed a vacuum-operated valve that directs air from the pump to the exhaust manifold or catalytic converter. Technician B accurately describes the function of the air bypass (AIRB) or diverter (AIRD) valve, which diverts the air pump output to the atmosphere or air filter during deceleration.

Question 7

The exhaust gas recirculation system reduces ______.

Accepted Answer

The exhaust gas recirculation (EGR) system primarily reduces oxides of nitrogen (NOx) emissions by recirculating a portion of an engine's exhaust gas back to the engine cylinders, diluting the oxygen in the incoming air stream and reducing the peak temperature during combustion.

Question 8

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?

Accepted Answer

Technician A is correct because the production of CO2 (carbon dioxide) is directly related to the amount of fuel burned; more fuel-efficient engines burn less fuel and thus produce less CO2. Technician B is correct because CAFE (Corporate Average Fuel Economy) standards aim to improve the average fuel economy of cars and light trucks sold in the United States, which would lead to reduced fuel consumption and thus lower CO2 emissions.

Question 9

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

Accepted Answer

The thermal vacuum valve (TVV) is not part of an enhanced (OBD-II) evaporative control system. OBD-II systems typically use electronic controls such as solenoid valves and sensors for managing evaporative emissions, rather than relying on thermal or vacuum-actuated components like the TVV.

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?

Accepted Answer

The EGR vent solenoid is typically normally open to allow the EGR system to vent when not in operation.

Question 11

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?

Accepted Answer

The canister purge solenoid valve is controlled during closed loop operation, not open loop. Technician B is correct because the system is designed to purge vapors without affecting drivability.

Question 12

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?

Accepted Answer

As the air/fuel ratio becomes richer, CO levels actually increase, not decrease. Technician B is correct in stating that CO is a colorless, odorless, and highly poisonous gas that can cause death.

Question 13

An I/M 240 test lasts _____ minutes.

Accepted Answer

The I/M 240 test, which stands for Inspection/Maintenance, lasts for four minutes. This test is used to measure a vehicle's emissions and overall performance under simulated driving conditions.

Question 14

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?

Accepted Answer

Both Technician A and Technician B are correct. A restricted or plugged PCV (Positive Crankcase Ventilation) valve can cause oil to enter the PCV filter and air cleaner, while oil buildup inside the throttle body can indicate high crankcase pressure, which is often a result of issues with the PCV system.

Question 15

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?

Accepted Answer

A three-way catalytic converter (TWC) is designed to facilitate a chemical reaction that oxidizes carbon monoxide (CO) and hydrocarbons (HC) into carbon dioxide (CO2) and water (H2O), as stated by Technician A. Additionally, it reduces nitrogen oxides (NOx) into nitrogen (N2) and carbon dioxide (CO2), as mentioned by Technician B. Therefore, both technicians are correct in their statements about the functions of a TWC.

Question 16

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?

Accepted Answer

Both Technician A and Technician B are correct. HC (hydrocarbon) emissions are indeed caused by incomplete combustion, and an excessively lean air/fuel mixture can lead to cylinder misfiring, which also results in high HC emissions.

Question 17

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

Accepted Answer

The OBD-II system is designed to detect leaks as small as 0.020 inches in the evaporative emission system.

Question 18

The AIR system reduces ______.

Accepted Answer

The AIR (Air Injection Reactor) system is designed to reduce emissions of hydrocarbons and carbon monoxide by injecting air into the exhaust stream, which helps to further combust these pollutants.

Question 19

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?

Accepted Answer

Both Technician A and Technician B are correct. The back pressure transducer can indeed be part of the EGR valve's design, allowing for more precise control of exhaust gas recirculation based on the pressure in the exhaust system. Technician B's statement about negative back pressure transducers using the vacuum in the exhaust between pressure pulses to modulate EGR flow is also accurate. This method helps in optimizing the EGR flow for better engine performance and reduced emissions.

Question 20

All the following are considered harmful gases EXCEPT:

Accepted Answer

O2 is not a harmful gas; it is essential for human life and is the molecular form of oxygen that we breathe.

Quiz 33: Emission Control Systems

The first controlled automotive emission was ______.

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?

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

The exhaust gas recirculation system reduces ______.

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?

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

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

An I/M 240 test lasts _____ minutes.

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 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 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?

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?

All the following are considered harmful gases EXCEPT:

Quiz 33: Emission Control Systems

The first controlled automotive emission was ______.

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?

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

The exhaust gas recirculation system reduces ______.

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?

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

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

An I/M 240 test lasts _____ minutes.

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 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 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?

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?

All the following are considered harmful gases EXCEPT:

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?

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?