Question 1

Some AIR systems will set a ___________________ in the PCM if there is a fault in the system.

Accepted Answer

The answer of Some AIR systems will set a ___________________...

Question 2

An exhaust ___________________ is one of the valuable diagnostic tools for driveability problems.

Accepted Answer

The answer of An exhaust ___________________ is one of the...

Question 3

A restricted or plugged ___________________ system may cause excessive HC and CO emissions.

Accepted Answer

The answer of A restricted or plugged ___________________ system may...

Question 4

In an engine in good condition running at 2,000 rpm, with a working EGR system, NO_X should be below _____ ppm.

Accepted Answer

The question is referring to the level of NOS (nitrous oxide), commonly referred to as NOx (nitrogen oxides). A properly functioning EGR (Exhaust Gas Recirculation) system helps to reduce NOx emissions by recirculating some of the engine's exhaust back into the intake. At 2,000 rpm, NOx emissions should be below 100 ppm (parts per million) to indicate a well-functioning engine with a working EGR system.

Question 5

A stuck open EGR valve could cause _____.

Accepted Answer

The answer of A stuck open EGR valve could cause...

Question 6

High ___________________ emissions are associated with an inoperative EGR valve.

Accepted Answer

The answer of High ___________________ emissions are associated with an...

Question 7

A dirty air filter may cause lower than normal ___________________ emissions.

Accepted Answer

The answer of A dirty air filter may cause lower...

Question 8

The customer complains of poor fuel economy. A five-gas analyzer reveals these measurements at 2,500 rpm: HC = 72 ppm, CO = 3.2%, CO₂ = 10.3%, O₂ = 0.2%, and NO_X = 122 ppm. What is the most likely cause?

Accepted Answer

The high CO (carbon monoxide) percentage indicates a rich fuel mixture. CO is produced in large amounts when there is too much fuel in the mixture and not enough oxygen for complete combustion.

Question 9

Technician A says a loose oil filler cap or a dip stick that is not fully seated in the dipstick tube can change the LTFT on a MAF system. Technician B says the PCV system will draw unfiltered air through these leaks which could result in premature wear of engine parts. Who is correct?

Accepted Answer

Both technicians are correct. A loose oil filler cap or a dipstick that is not fully seated can cause unmeasured air to enter the engine, resulting in a lean condition that can affect the long-term fuel trim (LTFT) on a MAF system. Additionally, the PCV system is designed to draw crankcase fumes into the intake manifold, so any unfiltered air that enters through these leaks can cause premature wear and tear on the engine components.

Question 10

Before the EVAP system on an OBD-II vehicle can be pressure tested or smoke tested for leaks, a scan tool must be used to _____.

Accepted Answer

Before performing a pressure test or smoke test on the EVAP system of an OBD-II vehicle, a scan tool must be used to close the canister vent solenoid. This action seals the system, allowing for accurate testing for leaks.

Question 11

Higher than normal ____________________ emissions may be caused by an overheated engine.

Accepted Answer

The answer of Higher than normal ____________________ emissions may be...

Question 12

Spark knock may be referred to as ____________________.

Accepted Answer

The answer of Spark knock may be referred to as...

Question 13

An excessively lean air/fuel ratio resulting in misfires causes HC emissions to ____________________.

Accepted Answer

The answer of An excessively lean air/fuel ratio resulting in...

Question 14

The first time the OBD-II system monitor detects a fault in the system, a ___________________ DTC is set. This will not cause the MIL light to illuminate and will self-erase if the monitor passes on the next trip.

Accepted Answer

The answer of The first time the OBD-II system monitor...

Question 15

Excessively high ____________________ emissions can be caused by any condition that prevents the EGR from allowing the correct amount of exhaust gases to enter the cylinders.

Accepted Answer

The answer of Excessively high ____________________ emissions can be caused...

Question 16

The OBD-II EGR system monitor tests the functioning of the EGR system by opening the EGR valve while monitoring the change in ______.

Accepted Answer

The OBD-II EGR system monitor tests the functioning of the EGR system by opening the EGR valve while monitoring the change in MAP voltage, EGR outlet temperature, and STFT.

Question 17

What tool is needed to test a digital EGR valve?

Accepted Answer

A scan tool is needed to test a digital EGR valve as it can communicate with the vehicle's computer to diagnose and test the EGR system.

Question 18

What tool is needed to test vacuum-type EGR valves?

Accepted Answer

A hand vacuum pump is used to test vacuum-type EGR valves by applying vacuum to see if the valve opens and closes properly.

Question 19

A rich air fuel mixture will cause high ____________________ emissions.

Accepted Answer

The answer of A rich air fuel mixture will cause...

Question 20

Technician A checks a PCV valve by sucking air through it with his mouth. Technician B checks a PCV valve by removing the valve from the grommet in the valve cover and placing his finger over the end of the valve to check for vacuum. Who is correct?

Accepted Answer

Technician A's method of checking the PCV valve by sucking air through it with his mouth is not safe and is not recommended. Technician B's method of removing the valve from the grommet in the valve cover and placing his finger over the end of the valve to check for vacuum is an appropriate method of checking the valve.

Quiz 34: Emission Control Diagnosis and Service