Emission Control System Testing, Service, and Repair

by
Russell Krick

Publisher

The Goodheart-Willcox Co., Inc.
Tinley Park, Illinois
© Goodheart-Willcox Co., Inc.

Permission granted to reproduce for educational use only


© Goodheart-Willcox Co., Inc.

Permission granted to reproduce for educational use only


(16 Topics)

 Computer-controlled emission system
service
 Emission maintenance reminder
 Inspecting emission control systems
 Exhaust gas analyzer
 Emissions testing programs
 Vacuum solenoid service
© Goodheart-Willcox Co., Inc.

Permission granted to reproduce for educational use only

 PCV system service
 Evaporative emissions control system
service
 Thermostatic air cleaner system service
 EGR system service
 Air injection system service
 Pulse air system service

© Goodheart-Willcox Co., Inc.

Permission granted to reproduce for educational use only


 Catalytic converter service
 Oxygen sensor service
 Emission control information sticker
 OBD II drive cycle

© Goodheart-Willcox Co., Inc.

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 Most emissions problems are caused
by a malfunction in a system unrelated
to the emission control system
 fuel system
 ignition system
 exhaust system
 computer control and electrical systems

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Permission granted to reproduce for educational use only


Scanning Emission
Systems
 Connect the scan tool to the data link
connector
 Check for diagnostic trouble codes
(DTC’s)
 Retrieve data

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Permission granted to reproduce for educational use only


Scanning Emission
Systems

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Scan Tool Readout
A. DTC
B. Description
C. Possible causes

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 The circuit turns on a dash light to
indicate the need for emission
control system service
 After repairs, the light must be
turned off
 Refer to the service manual for
numerous procedures
© Goodheart-Willcox Co., Inc.

Permission granted to reproduce for educational use only


Inspect vacuum hoses and wires
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Inspecting Vacuum
Hoses

Use a stethoscope to listen for
vacuum leaks
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Measures the chemical content of exhaust
gas
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Two-Gas Analyzer
 Measures two gases:
 hydrocarbons (HC)
 carbon monoxide (CO)

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Permission granted to reproduce for educational use only


Four-Gas Analyzer
 Measures four gases:
 hydrocarbons (HC)
 carbon monoxide (CO)
 carbon dioxide (CO2)
 oxygen (O2)

© Goodheart-Willcox Co., Inc.

Permission granted to reproduce for educational use only


Five-Gas Analyzer
 Measures five gases:
 hydrocarbons (HC)
 carbon monoxide (CO)
 carbon dioxide (CO2)
 oxygen (O2)
 oxides of nitrogen (NOx)

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Permission granted to reproduce for educational use only


Five-Gas Analyzer

Analyzer with a calibration gas
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Using a Gas Analyzer
 Warm-up the analyzer
 about 10 minutes

 Zero and calibrate the analyzer
 zero the meter while sampling shop air or

calibration gas

 Warm the vehicle to operating
temperature
 Insert a probe into the tail pipe through
a hole in the shop’s vent hose
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Permission granted to reproduce for educational use only


Analyzer Test
Procedures
 Two speed idle test
 idle and 2500 rpm

 Dynamometer test
 loads the engine to simulate actual
driving conditions

 Compare the readings to specifications

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Permission granted to reproduce for educational use only


Using a Gas Analyzer

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Exhaust Gas Analyzer
Readings

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Hydrocarbons
 HC
 Measured in parts per million (PPM) by
volume
 Unburned gasoline
 Newer vehicles have specifications of
approximately 220 PPM

© Goodheart-Willcox Co., Inc.

Permission granted to reproduce for educational use only


Carbon Monoxide
 CO
 Measured in percentage (%) by volume
 Indicates incomplete burning of fuel or
rich mixtures during combustion

caused by insufficient air or excess fuel
 Normal readings are below 1.5%

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Permission granted to reproduce for educational use only


Oxides of Nitrogen
 NOx
 Measured in parts per million (PPM) by
volume
 Formed when nitrogen and oxygen in
the cylinder combines
 Occurs when combustion chamber
temperatures are high

© Goodheart-Willcox Co., Inc.

Permission granted to reproduce for educational use only


Carbon Dioxide
 CO2
 Measured in percentage (%) by volume
 Byproduct of normal combustion that
occurs when one carbon atom
combines with two oxygen atoms
 Readings should be high, 8–15%

© Goodheart-Willcox Co., Inc.

Permission granted to reproduce for educational use only