Question 1

Where is air from the AIR pump directed when the engine is cold?
A) Air cleaner
B) Atmosphere
C) Catalytic converter
D) Exhaust manifold

Accepted Answer

When the engine is cold, air from the AIR (Air Injection Reaction) pump is directed to the exhaust manifold to help reduce emissions by promoting the oxidation of unburned hydrocarbons.

Question 2

An electric SAI pump is controlled by ________.
A) the PCM
B) a vacuum switch
C) exhaust pressure
D) manifold vacuum

Accepted Answer

The electric SAI (secondary air injection) pump is controlled by the PCM (powertrain control module) which receives input from various sensors such as the oxygen sensor and mass airflow sensor. The PCM sends a signal to the electric pump to turn on and inject air into the exhaust system to reduce emissions.

Question 3

Technician A says that the electric AIR pump requires periodic maintenance. Technician B says that if the AIR pump is good, the oxygen sensors should read 850 mV or more when the AIR pump is energized. Which technician is correct?
A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Accepted Answer

Electric AIR (Secondary Air Injection) pumps are generally maintenance-free, and the oxygen sensor reading of 850 mV or more when the AIR pump is energized is not a correct diagnostic criterion. Oxygen sensor voltages vary widely based on many factors, and this specific value does not directly indicate a properly functioning AIR pump.

Question 4

Technician A says that CO and HC levels should increase if the AIR hoses are pinched off. Technician B says that a defective drive belt may cause AIR system problems. Which technician is correct?
A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Accepted Answer

The AIR (Air Injection Reactor) system is designed to reduce emissions by injecting air into the exhaust stream to help burn off hydrocarbons (HC) and carbon monoxide (CO). If the AIR hoses are pinched off, it would restrict the flow of air into the exhaust, leading to increased levels of CO and HC due to incomplete combustion. A defective drive belt can lead to AIR system problems if the belt drives the air pump, as a malfunctioning pump would not inject air properly, also leading to increased emissions.

Question 5

Technician A says that the location of the catalytic converter is not important. Technician B says that the catalytic converter should be positioned as far from the engine as possible. Which technician is correct?
A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Accepted Answer

The location of the catalytic converter is important for its proper operation; it should be close enough to the engine to reach its operating temperature quickly but not so far as to cool the exhaust gases too much before treatment. Both technicians' statements are incorrect.

Question 6

At what temperature is the catalytic converter fully effective?
A) 100 deg F
B) 1000 deg F
C) 420 deg F
D) 500 deg F

Accepted Answer

Catalytic converters become fully effective at high temperatures, typically around 1000 degrees Fahrenheit (538 degrees Celsius), as they require heat to facilitate the chemical reactions that reduce exhaust emissions.

Question 7

A vehicle failed an emission test due to high carbon monoxide and hydrocarbons in the exhaust gas. What could be the cause?
A) Overfilling the fuel tank
B) Saturated EVAP charcoal canister
C) Either A or B
D) Neither A nor B

Accepted Answer

Overfilling the fuel tank can cause the fuel to enter into the EVAP system, saturating the charcoal canister, which leads to higher hydrocarbons in the exhaust gas. Therefore, either A or B can be the cause of high carbon monoxide and hydrocarbons in the exhaust gas.

Question 8

All of these are components of smog EXCEPT ________. A) AIR B) NO_x C) Fog D) HC

Accepted Answer

Air is not a component of smog. Smog is a type of air pollution that is caused by the reaction of sunlight with nitrogen oxides and hydrocarbons in the air.

Question 9

Smog contains ________, which is an irritant to lungs and eyes. A) CO₂ B) N₂ C) O₃ D) O₂

Accepted Answer

Ozone (O3), represented as option C (O₃), is a major component of smog and acts as an irritant to lungs and eyes.

Question 10

The OBD-II evaporative emission system monitor on a 2008 vehicle can detect a hole as small as ________.
A) 0.200" diameter
B) 0.020" diameter
C) 0.400" diameter
D) 0.040" diameter

Accepted Answer

The OBD-II evaporative emission system monitor on a 2008 vehicle can detect a hole as small as 0.020" diameter, which means option B is the correct answer.

Question 11

A leaking evaporative system can be diagnosed using ________.
A) Nitrogen gas and headphones
B) A smoke machine
C) Either of these
D) Neither of these

Accepted Answer

Both nitrogen gas and headphones and a smoke machine are common tools for diagnosing leaks in an evaporative system. Nitrogen gas can be used to pressurize the system without introducing moisture, and the headphones help listen for the escaping gas. A smoke machine introduces smoke into the system, and the smoke escaping from leaks makes them visible.

Question 12

An evaporative emission system leak detection pump adds ________ to the fuel tank in order to check for leaks.
A) slight pressure
B) pressure pulses
C) a vacuum
D) oxygen

Accepted Answer

An evaporative emission system leak detection pump adds slight pressure to the fuel tank in order to check for leaks. This is done to ensure the integrity of the fuel system and to prevent fuel vapors from escaping into the atmosphere, which could be harmful to the environment.

Question 13

A vacuum gauge is being used to check for a restricted exhaust system. The vacuum at idle is 18 in. Hg. Which of these results indicates a restriction?
A) Vacuum at 2,500 RPM is 22 in. Hg.
B) Vacuum at 2,500 RPM is 19 in. Hg.
C) Vacuum at 2,500 RPM is 9 in. Hg.
D) Not enough information to diagnose

Accepted Answer

A restricted exhaust system will cause a drop in vacuum as the engine RPM increases. Option C shows a significant drop in vacuum, indicating a restricted exhaust system. Option A shows an increase in vacuum, which is unlikely with a restricted exhaust system, and option B shows a minor drop in vacuum, which may be within normal limits. Option D cannot be chosen as there is enough information provided to diagnose.

Question 14

The catalytic converter stores, then burns oxygen.

Accepted Answer

The catalytic converter does not store or burn oxygen. It converts harmful pollutants in the exhaust gases into less harmful ones by using chemical reactions involving precious metals like platinum, palladium, and rhodium.

Question 15

This drawing shows a catalytic converter with exhaust gases entering the CAT. What are the gases changed to at the CAT outlet? A) HCO and CO B) NO_x C) H₂O and CO₂ D) Both A and C

Accepted Answer

The catalytic converter changes exhaust gas pollutants such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) into less harmful gases like water vapor (H2O), carbon dioxide (CO2), and nitrogen (N2). This is because the catalytic converter uses chemical reactions and precious metals like platinum, palladium, and rhodium as catalysts to break apart and recombine the harmful pollutants into less harmful ones. Therefore, the gases leaving the CAT outlet are likely water vapor, carbon dioxide, nitrogen, and possibly small amounts of oxygen (O2) or residual pollutants that were not fully converted. Choice A is incorrect because HCO is not a known gas component, and CO is partially correct but does not account for the full range of pollutants that the CAT can convert. Choice B is gibberish and not a valid answer option. Choice D is incorrect because CO and CO2 are both listed, and it is redundant to say both A and C when C already includes the answer from A.

Question 16

The O₂ sensors in this OBD II system are sending a voltage signal as shown. What conclusion can be made about the catalytic converter? A) The CAT is not working correctly B) The CAT is working correctly C) The engine is not running, so the CAT is not functioning D) Not enough information

Accepted Answer

The voltage signal from the O₂ sensors should oscillate between 0.1V and 0.9V. However, the graph shows a constant voltage near 0.9V, which indicates that the catalytic converter is not properly reducing the emissions and needs to be checked.

Quiz 27: Emission Control Devices Operation and Diagnosis

Where is air from the AIR pump directed when the engine is cold?

An electric SAI pump is controlled by ________.

Technician A says that the electric AIR pump requires periodic maintenance. Technician B says that if the AIR pump is good, the oxygen sensors should read 850 mV or more when the AIR pump is energized. Which technician is correct?

Technician A says that CO and HC levels should increase if the AIR hoses are pinched off. Technician B says that a defective drive belt may cause AIR system problems. Which technician is correct?

Technician A says that the location of the catalytic converter is not important. Technician B says that the catalytic converter should be positioned as far from the engine as possible. Which technician is correct?

At what temperature is the catalytic converter fully effective?

A vehicle failed an emission test due to high carbon monoxide and hydrocarbons in the exhaust gas. What could be the cause?

All of these are components of smog EXCEPT ________.

Smog contains ________, which is an irritant to lungs and eyes.

The OBD-II evaporative emission system monitor on a 2008 vehicle can detect a hole as small as ________.

A leaking evaporative system can be diagnosed using ________.

An evaporative emission system leak detection pump adds ________ to the fuel tank in order to check for leaks.

A vacuum gauge is being used to check for a restricted exhaust system. The vacuum at idle is 18 in. Hg. Which of these results indicates a restriction?

The catalytic converter stores, then burns oxygen.

This drawing shows a catalytic converter with exhaust gases entering the CAT. What are the gases changed to at the CAT outlet?

The O2 sensors in this OBD II system are sending a voltage signal as shown. What conclusion can be made about the catalytic converter?

The O₂ sensors in this OBD II system are sending a voltage signal as shown. What conclusion can be made about the catalytic converter?