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.
NOTE:
Before replacing ECM use ohmmeter and check resistance of each ECM controlled relay and solenoid coil. See ECM wiring diagram for coil terminal identification for solenoid(s) and relay(s) to be checked. Replace any relay or solenoid if the coil resistance measures less than 20 ohms.