emissions control automotive repair technician 5 : engine

Automotive Repair Technician 5 : EngineEmissions Control

Lesson 3 Overview

In this lesson, you'll cover

the many different systems

used for engine emission

control. You'll learn about

evaporative emissions,

exhaust gas recirculation

(EGR), positive crankcase

ventilation (PCV), SAI

(Secondary Air Injection),

and catalytic converters.

3.1 Identify emissions standards in the United Statesand elsewhere in the worldEmission Standards

READING ASSIGNMENT

Read this assignment. Then read Chapter 82 in your textbook.

Vehicle Emission Standards and Testing

Chapter 82 discusses emissions standards in the United States and

Copyright Penn Foster, Inc. 2019 Course Version: 1

elsewhere in the world and explains exhaust analysis testing

procedures. Lastly, it identifies the reasons for excessive emission of

hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen

(NOx)

The following videos and animation links from the author’s website will

help you better understand the textbook and your assignments.

Emission Standards (www.jameshalderman.com/links/book_at/vi

d/ch82/video_frame.html)

The emission control systems (ECS) label is under the hood of every

vehicle produced for sale in the United States; it details information

about the emissions system originally installed in the vehicle. If a

vehicle is damaged in a collision, the ECS label may not be replaced

during body repair. A replacement ECS label can be obtained using

information from the vehicle identification number (VIN).

Use the Internet to research the Clean Air Act and the reasoning

behind exhaust emission control in cars and light trucks.

Key Points and Link

READING ASSIGNMENT

Key Points

The emission control systems (ECS) label is under the hood of

every vehicle produced for sale in the United States; it details

information about the emissions system originally installed in the


http://www.jameshalderman.com/links/book_at/vid/ch82/video_frame.html

vehicle.

If a vehicle is damaged in a collision, the ECS label may not be

replaced during body repair.

A replacement ECS label can be obtained using information from

the vehicle identification number (VIN).

Link

Emission Standards (www.jameshalderman.com/links/book_at/vi

d/ch82/video_frame.html)

Emission Standards

1. The causes of a/an _________ exhaust mixture include a

defective fuel-pressure regulator, a leaking injector, a stuck-open

pump valve, or a clogged air intake.

2. Technician A says that high HC emission levels are often caused

by a fault in the ignition system. Technician B says that high CO2

emissions are usually caused by a richer-than-normal air-fuel

mixture. _______ is/are correct.

a. Technician A only

b. Technician B only

c. Both Technician A and B

d. Neither Technician A nor B

3. High HC and CO emissions and low CO2 and O2 emissions may

be caused by a _______.



a. rich mixture

b. lean mixture.

c. defective ignition component.

d. clogged EGR passage.

4. Which of the following is generally considered to be the rich

indicator?

a. Hydrocarbons

b. Carbon monoxide

c. Carbon dioxide

d. Oxygen

5. Which of the following is generally considered to be the lean

indicator?

a. Hydrocarbons

b. Carbon monoxide

c. Carbon dioxide

d. Oxygen

6. Technician A says that carbon inside the engine can cause

excessive NOx to form. Technician B says that excessive NOx

could be caused by a cooling system fault, causing the engine to

get too hot. _______ is/are correct.



c. Both Technician A and B


Exercise Answer Key:


Emission Standards

1. rich

2. a

3. a

4. b

5. d

6. c

3.2 Define the operation of enhanced and nonenhancedevaporative control (EVAP) and exhaust gasrecirculation (EGR) systemsEVAP and EGR

READING ASSIGNMENT

Read this assignment. Then read Chapters 83 and 84 in your textbook.

Evaporative Emission Control Systems

Chapter 83 discusses the operation of an evaporative emission control

system, comparing the different types—enhanced and nonenhanced

evaporative control (EVAP) systems, leak detection pump systems,

and onboard refueling vapor recovery (ORVR) systems. This chapter

also explains how to diagnose the EVAP system, the functions of an

evaporative system monitor, and how to interpret EVAP diagnostic

trouble codes.


The following videos and animation links from the author’s website

may help you better understand the textbook and your assignments.

Evaporative Control Systems (www.jameshalderman.com/links/b

ook_at/vid/ch83/video_frame.html)

Evaporative Emission Control System (jameshalderman.com/link

s/a8/html5/evap_control.html)

You can remember the rest position of both purge and vent

solenoids—normally closed and normally open, respectively—

with the analogy of a home’s front and back doors. Whereas the

front door is usually closed, the back door is frequently left open.

Vent solenoids can be tested using jumper wires and a 12-volt

source, such as the vehicle battery. The vent solenoid is NO

(normally open) and should be energized for periods no longer

than 5 minutes to prevent damage.

The powertrain control module (PCM) on a vehicle that uses an

engine-off natural vacuum for evaporative system testing must

stay on, operating long after the ignition has been shut off, to

satisfactorily test evaporative system integrity. You shouldn’t

overlook this capability when diagnosing a battery drain.

Exhaust Gas Recirculation Systems

Chapter 84 discusses the purpose and function of exhaust gas

recirculation (EGR) systems and explains the strategies for monitoring

OBD-II EGR systems. The chapter also covers how to diagnose a

defective EGR system as well as how to interpret EGR-related OBD-II



http://jameshalderman.com/links/a8/html5/evap_control.html

trouble codes.

Search the Internet to learn more about the purpose of computer

OBD-II monitors.



EGR System (www.jameshalderman.com/links/book_at/vid/ch84/

video_frame.html)

Exhaust Gas Recirculation (jameshalderman.com/links/a8/html5/

exhaust_gas_recirculation_operation.html)

The speed-density fuel system, which uses MAP and TP sensors to

detect engine load, can be fooled by a stuck-open EGR valve. Such a

valve admits exhaust pressure into the intake manifold, which the

PCM misinterprets as an increase in engine load. This in turn leads to

a very rich mixture in the fuel system.

Excess exhaust will cause the engine to run poorly. In addition, black

exhaust smoke caused by this overly rich condition may prompt the

technician to mistakenly look for a fuel-system problem.

Research to find out when the first EGR valve was used and for what

reason.

EGR Sensor Circuit and DTC Diagnosis

Search the Internet to locate and print out a wiring diagram for an



http://jameshalderman.com/links/a8/html5/exhaust_gas_recirculation_operation.html

EGR circuit. Highlight the circuit and note any areas that could set off

the type of DTC outlined on page 941 of your textbook.

Key Points and Links

READING ASSIGNMENT

Key Points

You can remember the rest position of both purge and vent

solenoids—normally closed and normally open, respectively—

with the analogy of a home’s front and back doors. Whereas the

front door is usually closed, the back door is frequently left open.

Vent solenoids can be tested using jumper wires and a 12-volt

source, such as the vehicle battery. The vent solenoid is NO

(normally open) and should be energized for periods no longer

than 5 minutes to prevent damage.

The powertrain control module (PCM) on a vehicle that uses an

engine-off natural vacuum for evaporative system testing must

stay on, operating long after the ignition has been shut off, to

satisfactorily test evaporative system integrity. You shouldn’t

overlook this capability when diagnosing a battery drain.

Excess exhaust will cause the engine to run poorly. In addition,

black exhaust smoke caused by this overly rich condition may

prompt the technician to mistakenly look for a fuel-system

problem.

Links


Evaporative Control Systems (www.jameshalderman.com/links/b

ook_at/vid/ch83/video_frame.html)

Evaporative Emission Control System (jameshalderman.com/link

s/a8/html5/evap_control.html)

EGR System (www.jameshalderman.com/links/book_at/vid/ch84/

video_frame.html)

Exhaust Gas Recirculation (jameshalderman.com/links/a8/html5/

exhaust_gas_recirculation_operation.html)

EVAP and EGR

1. The components in a typical evaporative control system include

the carbon canister, purge valve, ________, and connecting

hoses/connections.

2. The computer controls the purging of the vapor canister by

turning the ________ on and off.

3. Nonenhanced EVAP systems aren’t capable of detecting leaks in

the system, whereas ________ systems are able to do this.

4. Oxides of nitrogen are created under high pressure, or

temperatures over ________ inside the combustion chamber.

5. Depending on the make of vehicle, the PCM may use one of the

following to detect EGR flow: monitoring the _______ sensor or



http://jameshalderman.com/links/a8/html5/evap_control.html


http://jameshalderman.com/links/a8/html5/exhaust_gas_recirculation_operation.html

the ________ sensor when commanding the EGR to open.

6. Technician A says that a low-restriction exhaust system could

prevent a back pressure-type vacuum-controlled EGR valve from

opening correctly. Technician B says that restricted exhaust can

cause the EGR valve position sensor to fail. _______ is/are

correct.



c. Both Technicians A and B


7. EGR is used to control _______.

a. unburned hydrocarbons.

b. oxides of nitrogen.

c. carbon monoxide

d. both b and c.

8. The ________ valve is subject to rust and corrosion more than

any of the others.

a. purge

b. vacuum control

c. vent

d. roll-over check


EVAP and EGR

1. vent valve


2. purge solenoid

3. enhanced

4. 2,500 °F (1,370 °C)

5. oxygen, MAP

6. c

7. b

8. c

3.3 Describe the purpose and function of positivecrankcase ventilation (PCV) systems, the secondary air-injection (SAI) systems, and catalytic convertersPCV, SAI, and Catalytic Converters

READING ASSIGNMENT

Read this assignment. Then read Chapters 85 and 86 in your textbook.

Positive Crankcase Ventilation and Secondary Air-Injection Systems

Chapter 85 discusses the purpose and function of the positive

crankcase ventilation (PCV) system and the secondary air-injection

(SAI) system. The chapter also explores how to diagnose faults in

these systems.




PVC and SAI System (www.jameshalderman.com/links/book_at/v

id/ch85/video_frame.html)

Positive Crankcase Ventilation (PCV ) (jameshalderman.com/link

s/a8/html5/pos_crank_vent_2.html)

Secondary Air-Injection (jameshalderman.com/links/a8/html5/Sec

ondary_Air-Inject-Chapter_85-A8.html)

Don’t overlook a malfunctioning PCV system when diagnosing

excessive oil leaks. A plugged PCV system can create excess

pressure in the crankcase due to an accumulation of combustion

vapors. This excess pressure can force oil out of the crankcase

through engine seals and gaskets. (See Figure 85-6 on page 945 of

your textbook.)

Research to learn more about the use of secondary air-injection

systems, when they were first used, and whether they’re still used

today.

PCV Rattle Test

Using the procedure on textbook page 944 as your guide, perform the

rattle test on your car.

SAI Circuit and DTC Diagnosis

Search the Internet to locate and print out a wiring diagram for a

secondary air-injection (SAI) system circuit. Highlight the circuit and

note any areas that could set off DTC P0410, an SAI solenoid circuit



http://jameshalderman.com/links/a8/html5/pos_crank_vent_2.html

http://jameshalderman.com/links/a8/html5/Secondary_Air-Inject-Chapter_85-A8.html

failure, as outlined on page 947 of your textbook.

Catalytic Converters

Chapter 86 explains the purpose, function, construction, operation,

and diagnosis of catalytic converters.

The following videos and animation links from the author’s website will

help you better understand the textbook and your assignments.

Catalytic Converter (www.jameshalderman.com/links/book_at/vid/

ch82/video_frame.html)

Catalytic Converter Operation (jameshalderman.com/links/a8/htm

l5/Cat_Conv_Op_A8_Chapter_86.html)

Catalytic Converter (2004+) (jameshalderman.com/links/a8/html5

/catalytic_converter.html)

Because the prices of precious metals used in catalytic converters

have risen steeply in the past few years, these components have

become popular targets of thieves. So be wary: just because an

aftermarket catalytic converter fits a particular vehicle doesn’t mean it

will control the emissions of that vehicle. An aftermarket converter sold

at a reduced price likely doesn’t contain the necessary amount of the

crucial precious metal cerium. This can cause a vehicle to fail state

emissions tests or continually indicate an emissions defect. See

Figure 86-12 on page 953 of your textbook for more about this

problem.

Search the Internet to determine the cost of a catalytic converter.



http://jameshalderman.com/links/a8/html5/Cat_Conv_Op_A8_Chapter_86.html

http://jameshalderman.com/links/a8/html5/catalytic_converter.html

Catalytic Converter Diagnosis

Catalytic Converter

Temperature

Measuring the Catalytic

Converter Temperature with an

Infrared Thermometer

(Courtesy of Jim Halderman)

This exercise will require a noncontact infrared thermometer with laser

targeting, which can be rented or purchased from various dealers

online and elsewhere. Operate your vehicle engine at 2,500 RPM until

normal operating temperature is achieved. Then measure the inlet

and outlet temperatures of the catalytic converter with the infrared

thermometer as shown in the figure.

Key Points and Links

READING ASSIGNMENT


Key Points

A plugged PCV system can create excess pressure in the

crankcase due to an accumulation of combustion vapors. This

excess pressure can force oil out of the crankcase through

engine seals and gaskets.

Just because an aftermarket catalytic converter fits a particular

vehicle doesn’t mean it will control the emissions of that vehicle.

Links

PCV and SAI System (www.jameshalderman.com/links/book_at/v

id/ch85/video_frame.html)

Positive Crankcase Ventilation (PCV ) (jameshalderman.com/link

s/a8/html5/pos_crank_vent_2.html)

Secondary Air-Injection (jameshalderman.com/links/a8/html5/Sec

ondary_Air-Inject-Chapter_85-A8.html)

Catalytic Converter (www.jameshalderman.com/links/book_at/vid/

ch82/video_frame.html)

Catalytic Converter Operation (jameshalderman.com/links/a8/htm

l5/Cat_Conv_Op_A8_Chapter_86.html)

Catalytic Converter (2004+) (jameshalderman.com/links/a8/html5

/catalytic_converter.html)

PCV, SAI, and Catalytic Converters

1. Both PCV and SAI systems are used to reduce HC and



http://jameshalderman.com/links/a8/html5/pos_crank_vent_2.html

http://jameshalderman.com/links/a8/html5/Secondary_Air-Inject-Chapter_85-A8.html


http://jameshalderman.com/links/a8/html5/Cat_Conv_Op_A8_Chapter_86.html

http://jameshalderman.com/links/a8/html5/catalytic_converter.html

________ emissions.

2. The ________ valve works by regulating airflow through the

crankcase under all operating conditions.

3. Technician A says that if the PCV valve is defective or clogged,

the engine could idle rough. Technician B says that the engine

may stall. _______ is/are correct.

a. Technician A

b. Technician B



4. Technician A says that a PCV valve that rattles is fine and

doesn’t need to be replaced. Technician B says that if a PCV

valve doesn’t rattle, it should be replaced. _______ is/are correct.

a. Technician A

b. Technician B



5. Technician A says that the PCV system should create a slight

pressure in the crankcase at idle. Technician B says that the PCV

system should create a slight vacuum in the crankcase at 2,500

RPM. _______ is/are correct.

a. Technician A

b. Technician B




6. Rhodium, palladium, and ________ are used in most catalytic

converters.

7. The PCM monitors the catalytic converter’s efficiency by checking

the downstream oxygen sensor switch rates to the upstream

oxygen sensor switch rates. If the switch rates are similar, the

catalytic converter efficiency is _______.

8. Which of the following is applied to the ceramic substrate to make

the surface porous?

a. Honeycomb filler

b. Washcoat

c. Aluminum

d. Cerium

9. Two technicians are discussing catalytic converters. Technician A

says that the exhaust mixture must fluctuate between rich and

lean for the best efficiency. Technician B says that the air-fuel

mixture must be leaner than 14.7:1 for best performance from a

three-way catalytic converter. _______ is/are correct.

a. Technician A

b. Technician B




PCV, SAI, and Catalytic Converters

1. CO


2. PCV

3. a

4. b

5. b

6. platinum

7. low

8. b

9. a

Lesson 3 Review

Self-Check

1. Which of these is an intermediate California standard that is about

twice as stringent as tier 1 for HC and NOX?

a. Zero-Emission Vehicle (ZEV)

b. Ultra-Low-Emission Vehicle (ULEV)

c. Low-Emission Vehicle (LEV)

d. Transitional Low-Emission Vehicle (TLEV)

2. These federal emission standards are set by the _______ of 1990,

which are grouped by tier.

a. European Standards

b. California Standards

c. Smog Emission Information


d. Clean Air Act Amendments (CAAA)

3. The _______ is the test used to certify all new vehicles before they

can be sold.

a. one-speed and two-speed idle test

b. Federal Test Procedure

c. loaded mode test

d. SHED test

4. Which type of test uses a dynamometer that applies a heavy load

on the vehicle at a steady-state speed?

a. Loaded mode test

b. Acceleration Simulation Mode

c. One-speed and two-speed idle test

d. I/M 240 test

5. During engine operation, stored vapors are drawn from the canister

into the engine through a hose connected to the throttle body or the air

cleaner. This is called

a. vapor purging.

b. trap and hold.

c. air intake.

d. controlled release.

6. The most efficient method of leak detection in the evaporation

system is to introduce _______ under low pressure from a machine

specifically designed for this purpose.

a. water

b. CO2

c. nitrogen gas


d. smoke

7. _______ is an effective vapor trap because of its great surface

area.

a. Sand

b. Activated charcoal

c. Copper wools

d. Stainless wools

8. 28 inches H2O equals how many PSI?

a. 4

b. 1

c. 3

d. 2

9. _______ is an emission control system that lowers the amount of

nitrogen oxides (NOX) formed during combustion.

a. Open flow modulator (OFM)

b. Exhaust Gas Recirculation (EGR)

c. Acceleration Simulation Mode (ASM)

d. Evaporative Control (EVAP)

10. EGR is usually required during which of these conditions?

a. At wide open throttle

b. Maintaining a consistent speed

c. When the engine is cold

d. During idle speed

11. In addition to lowering NOX levels, the EGR system also helps

control

a. carbon dioxide.


b. unburned hydrocarbons.

c. detonation.

d. carbon monoxide.

12. Most vehicles today use the _______ to operate the EGR system.

a. delta pressure feedback EGR sensor.

b. pressure feedback EGR sensor

c. powertrain control module

d. EGR valve position sensor

13. This process of gases leaking past the rings is called

a. reaction.

b. ventilation.

c. blow.

d. blowby.

14. What test involves removing the oil-fill cap, starting the engine,

and holding a piece of paper over the opening?

a. Crankcase vacuum

b. 3 x 5 card

c. Rattle

d. Snap-back

15. The _______ system provides the air necessary for the oxidizing

process either at the exhaust manifold or inside the catalytic

converter.

a. crankcase

b. secondary air-injection

c. separator

d. orifice-control


16.

The _______ style of air pump is generally used only during cold

engine operation and is computer controlled.

a. inlet air filter

b. electrIc motor-drIven

c. external

d. belt-driven

17. Which of these causes of premature catalytic converter failure is

characterized by substances that can destroy the converter, such as

engine oil?

a. Excessively lean fuel mixtures

b. Improper air-fuel mixtures

c. Contamination

d. Excessive temperatures

18. A _______ is a chemical that helps start a chemical reaction but

does not enter into the chemical reaction.

a. cause agent

b. catalyst

c. change agent

d. converter

19. A catalytic converter must be located _______ the exhaust

manifold to work effectively.

a. 2 inches from

b. as close as possible to

c. 12 inches from

d. as far as possible from


20. What test for diagnosing catalytic converters

involves tapping gently on the catalytic converter using a rubber

mallet?

a. Test for back pressure with a vacuum gauge

b. Cycling sensor test

c. Test for back pressure with a pressure gauge

d. Tap test

Self-Check Answer Key

1. Low-Emission Vehicle (LEV)

Explanation: Low-Emission Vehicle (LEV), also known as LEV I is

an intermediate California standard about twice as stringent as

tier 1 for HC and NOX.

Reference: Section 3.1

2. Clean Air Act Amendments (CAAA)

Explanation: Federal emission standards are set by the Clean Air

Act Amendments (CAAA) of 1990, which are grouped by tier.


3. Federal Test Procedure

Explanation: The Federal Test Procedure (FTP) is the test used

to certify all new vehicles before they can be sold. Once a vehicle

meets these standards, it is certified by the EPA for sale in the

United States.



4. Acceleration Simulation Mode

Explanation: The Acceleration Simulation Mode test uses a

dynamometer that applies a heavy load on the vehicle at a

steady-state speed. The load applied to the vehicle is based on

the acceleration rate on the second simulated hill of the FtP.


5. vapor purging.

Explanation: During engine operation, stored vapors are drawn

from the canister into the engine through a hose connected to the

throttle body or the air cleaner. This vapor purging process mixes

unburned gasoline vapors from the canister with the existing air-

fuel charge.


6. smoke

Explanation: The most efficient method of leak detection in the

evaporation system is to introduce smoke under low pressure

from a machine specifically designed for this purpose.


7. Activated charcoal

Explanation: Activated charcoal is an effective vapor trap

because of its great surface area.



8. 1

Explanation: 28 inches H2O equals 1 pound per square inch, or 1

PSI. Pressures can build inside the fuel system and are usually

measured in units of inches of water, abbreviated “in. H2O”


9. Exhaust Gas Recirculation (EGR)

Explanation: Exhaust Gas Recirculation (EGR) is an emission

control system that lowers the amount of nitrogen oxides (NOx)

formed during combustion.


10. Maintaining a consistent speed

Explanation: EGR is usually required when maintaining a

consistent speed. EGR is usually not required during the following

conditions because the combustion temperatures are low:

During idle speed

When the engine is cold

At wide-open throttle (WOT) (Not allowing EGR allows the

engine to provide extra power when demanded. While the

NOX formation is high during these times, the overall effect

of not using EGR during WOT conditions is minor.)



11. detonation.

Explanation: In addition to lowering NOX levels, the EGR system

also helps control detonation.


12. powertrain control module

Explanation: Most vehicles today use the powertrain control

module (PCM) to operate the EGR system.


13. blowby.

Explanation: This process of gases leaking past the rings is

called blowby.


14. 3 x 5 card

Explanation: The 3 x 5 card test involves removing the oil-fill cap,

starting the engine, and holding a piece of paper over the

opening.


15. secondary air-injection

Explanation: The secondary air-injection (SAI) system provides

the air necessary for the oxidizing process either at the exhaust

manifold or inside the catalytic converter.



16. electrIc motor-drIven

Explanation: The electrIc motor-driven air style of pump is

generally used only during cold engine operation and is computer

controlled.


17. Contamination

Explanation: Contamination is caused by substances that can

destroy the converter including exhaust that contains excess

engine oil, antifreeze, sulfur (from poor fuel), and various other

chemical substances. Contamination is a cause of premature

converter failure.


18. catalyst

Explanation: A catalyst is a chemical that helps start a chemical

reaction but does not enter into the chemical reaction.


19. as close as possible to

Explanation: A catalytic converter must be located as close as

possible to the exhaust manifold to work effectively.



20. Tap test

Explanation: The simple tap test involves tapping gently on the

catalytic converter using a rubber mallet. If the substrate inside

the converter is broken, the converter will rattle when hit. If the

converter rattles, a replacement converter is required.


Flash Cards

1. Term: Acceleration Simulation Mode (ASM)

Definition: Uses a dynamometer that applies a heavy load on the

vehicle at a steady-state speed. The load applied to the vehicle is

based on the acceleration rate on the second simulated hill of the

FTP. This acceleration rate is 3.3 mph/sec/sec.

2. Term: Federal Test Procedure (FTP)

Definition: The test used to certify all new vehicles before they can be

sold

3. Term: Clean Air Act Amendments (CAAA)

Definition: Federal emission standards set by the CAAA of 1990

grouped by tier. All vehicles sold in the United states must meet tier 1

standards.

4. Term: Lean Indicator

Definition: The amount of leftover oxygen coming out of the tailpipe is


an indication of leanness. The higher the 02 level, the leaner the

exhaust.

5. Term: Rich Indicator

Definition: Excessive carbon monoxide is an indication of too rich an

air-fuel mixture. The higher the CO reading, the richer the air-fuel

mixture.

6. Term: Smog

Definition: Smoke and fog; created when sunlight reacts chemically

with NOX and unburned hydrocarbons (HC)

7. Term: Ozone

Definition: An enriched oxygen molecule with three atoms of oxygen

(O3) instead of the normal two atoms of oxygen (O2)

8. Term: Evaporative Control (EVAP) System

Definition: Traps and holds gasoline vapors. The EVAP system

includes the charcoal canister, hoses, and valves; vapors are burned

in the engine instead of being released into the atmosphere.

9. Term: Leak Detection Pump (LDP)

Definition: Part of the evaporative control system diagnosis

equipment. The vent valve in the lDP is normally open. Filtered fresh

air is drawn through the lDP to the canister. The lDP uses a spring

attached to a diaphragm to apply pressure.


10. Term: Onboard Refueling Vapor Recovery (ORVR)

Definition: Contains vapors from releasing into the atmosphere using

the restricted tank filler tube which tends to draw outside air into the

filler tube.

11. Term: Exhaust Gas Recirculation (EGR)

Definition: An emission control system that lowers the amount of

nitrogen oxides (NOX) formed during combustion

12. Term: Digital EGR Valve

Definition: Consists of three solenoids—small, medium, and large—

controlled by the powertrain control module (PCM)

13. Term: Delta Pressure Feedback EGR (DPFE) Sensor

Definition: Measures the pressure differential between two sides of a

metered orifice positioned just below the EGR valve’s exhaust side.

Pressure between the orifice and the EGR valve decreases when the

EGR opens.

14. Term: Positive Crankcase Ventilation (PCV) Systems

Definition: Developed to ventilate the crankcase and recirculate the

vapors to the engine’s induction system so they can be burned in the

cylinders

15. Term: Secondary Air-Injection (SAI) System


Definition: Provides the air necessary for the oxidizing process either

at the exhaust manifold or inside the catalytic converter

16. Term: Smog Pump

Definition: Pulls fresh air in through an external filter and pumps the

air under slight pressure to each exhaust port through connecting

hoses or a manifold

17. Term: Catalytic Converter

Definition: An after-treatment device used to reduce exhaust

emissions outside of the engine

18. Term: Catalyst

Definition: A chemical that helps start a chemical reaction but doesn't

enter into the chemical reaction

19. Term: Three-way (Catalytic) Converter (TWC)

Definition: All three exhaust emissions (NOX, HC, and Co) are

converted to carbon dioxide (CO2) and water (H2O).


emissions control automotive repair technician 5 : engine

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