Engine Emission Control

The engine emission control system consists of the:

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

Item	Part Number	Description
1	-	Adjustment procedure notes
2	-	Ignition timing specifications
3	-	Engine vacuum hose routing (typical)
4	-	Spark plug gap specifications
5	-	Engine type

The VECI decal shows:

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

Refer to IDENTIFICATION CODES article.

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

Item	Part Number	Description
1	12A650	Powertrain control module
2	9Y456	EGR system module
3	9D477	EGR system module-to-exhaust manifold tube

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 system module-to-exhaust manifold tube and sends a signal to the powertrain control module.

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 system module-to-exhaust manifold tube:

• connects the exhaust manifold to the EGR valve.

The EGR system module transducer:

• monitors the EGR system module flow rate through the EGR to exhaust manifold tube.
• sends an EGR system module flow rate signal to the powertrain control module.
• provides barometric pressure reading at key-on.

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