EGR System

An ECM-controlled solenoid valve is used to control EGR valve function. This valve is located in the vacuum line to the EGR valve and is operated by the ECM in response to coolant temperature, throttle position, and manifold pressure.

Under conditions of low coolant temperature, engine cranking, wide open throttle, or engine idle, the solenoid valve is de-energized, blocking vacuum to the EGR valve. At normal operating temperature with engine speed above idle, the solenoid valve is energized, allowing normal EGR valve function.

Two EGR valves and systems are used depending upon vehicle weight and engine application. Vehicles under 8500 GVW with 2.5L, 4.3L, 5.0L or 5.7L engines use a negative backpressure EGR valve with ECM-controlled solenoid valve. Vehicles over 8500 GVW with 2.8L, 5.7L or 7.4L engines use a ported EGR valve with ECM-controlled solenoid valve. In addition, 2.8L engine vehicles use an EGR vacuum switch to monitor vacuum to the EGR valve.