Engine Emission Control

Engine Emission Control

NOTE: Do not permanently remove or render inoperative any part of the vehicle emission control system including related hardware. Failure to comply may violate applicable state and federal laws.

The engine emission control system consists of the:

- EGR system.
- PCV system.
- Secondary Air Injection (AIR) system.

EGR System

The EGR system returns a small amount of exhaust gas into the intake manifold. This reduces the overall combustion temperature. Cooler combustion temperatures provide a significant reduction of the Nitrogen Oxides (NOX) in the exhaust emissions.

The engine incorporates a stepper motor-controlled EGR valve which receives its signal from the PCM. Engine coolant is used to cool the EGR valve. The EGR valve and stepper motor are serviced as an assembly.

The amount of recirculated exhaust gas depends on:

- engine rpm.
- intake manifold vacuum.
- exhaust backpressure.
- Engine Coolant Temperature (ECT).
- Throttle Position (TP).

PCV System

The PCV system uses intake manifold vacuum to ventilate blow-by vapors from the crankcase and return the vapors to the intake manifold for combustion. The PCV valve varies the amount of blow-by vapors returned to the intake manifold based on available engine vacuum. The PCV valve also prevents backfiring into the crankcase.

Secondary Air Injection (AIR) System

The AIR system controls emissions during engine operation by forcing air downstream into the exhaust manifold to oxidize the hydrocarbons and carbon monoxide.


Vehicle Emission Vacuum Routing

Partial Zero Emissions Vehicle (PZEV)











Non PZEV