Engine Emission Control (Description and Operation)

CAUTION: Do not remove any part of the engine emission control system. Operating the engine without the engine emission control system will reduce fuel economy and engine ventilation. This will weaken engine performance and shorten engine life.

The engine emission control consists of the:

• positive crankcase ventilation (PCV) system.
• exhaust gas recirculation (EGR) system.

Typical Vehicle Emission Control Information (VECI) Decal

The Vehicle Emission Control Information (VECI) decal shows:

• the components of the emission control system.
• the correct vacuum hose routing.
• the color stripe of the vacuum hoses.

The PCV system uses the intake manifold vacuum to ventilate the crankcase and return the fumes to the intake manifold for combustion.

EGR System Components

The EGR system returns a portion of the exhaust gas to the intake manifold to reduce the combustion temperature. This results in lower nitrous oxide formation.

The powertrain control module (PCM) controls the EGR vacuum regulator solenoid . The EGR vacuum regulator solenoid controls the vacuum to the EGR valve. When the EGR valve opens, exhaust gas flows to the intake manifold. The EGR transducer measures the flow through the EGR valve to exhaust manifold tube and sends a signal to the powertrain control module. A metering orifice in the EGR valve to exhaust manifold tube restricts the flow rate when the EGR valve is open.

The PCV valve:

• controls the amount of ventilating air and blow-by gases going to the intake manifold.
• prevents a backfire from reaching the crankcase.

The EGR valve to exhaust manifold tube:

• connects the exhaust manifold to the EGR valve.
• has two tubes connecting to the EGR transducer for EGR flow monitoring.

The EGR transducer:

• monitors the EGR flow rate through the EGR valve to exhaust manifold tube.
• sends an EGR flow rate signal to the powertrain control module.

The EGR vacuum regulator solenoid uses input from the powertrain control module to change the EGR valve operation.

Engine Emission Control (DIAGNOSIS AND TESTING)

Refer to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.

• Typical Vehicle Emission Control Information (VECI) Decal
• EGR System Components