Chart C7 - EGR Check
The ECM operates a solenoid to control the EGR valve. This solenoid is normally closed. By providing a ground path, the ECM energizes the solenoid which then allows vacuum to pass to the EGR valve. The ECM control of the EGR is based on the following inputs:
- Engine coolant temperature above 25°C.
- TPS idle.
- MAP.NOTE: Test numbers refer to test numbers on diagnostic chart.
- Checks for a stuck open solenoid.
- Checks for solenoid always being energized.
- Grounding test terminal should energize solenoid and vacuum should drop.
- Negative backpressure valve should hold vacuum with the engine off.
- When the engine is started, exhaust backpressure should cause vacuum to bleed off and valve to fully close.
- The 4.3L engines have a manifold vacuum source which should have at least 7 in. Hg of vacuum at idle.