Vacuum Diaphram EGR Valve

EGR System Check:

CIRCUIT DESCRIPTION:

The EGR Valve is controlled by a normally closed solenoid. The ECM pulses the solenoid to turn "ON" and regulate the EGR. The ECM diagnoses the system using an internal EGR test procedure. The ECM control of the EGR valve is based on the following inputs:

^ Engine coolant temperature - above 25~C.
^ TPS - "OFF" idle
^ MAP

Code 32 will detect a faulty solenoid, vacuum supply, EGR Valve or plugged passage. This chart checks for plugged EGR passages, a sticking EGR valve, or a stuck open or inoperative solenoid.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. With the ignition "ON," engine stopped, the solenoid should not be energized and vacuum should not pass to the EGR valve.

2. Grounding the diagnostic test terminal should energize solenoid and allow vacuum to pass to the EGR valve.

3. Checks for plugged EGR passages. If passages are plugged, the engine may have severe detonation problems on acceleration.

4. The vehicle must be driven during this test to produce sufficient engine load to operate the EGR. Lightly accelerating (approximately 1/4 throttle) will produce a large and stable enough reading to determine if the ECM is commanding the system "ON."

DIAGNOSTIC AIDS:

^ Before replacing ECM use ohmmeter and check resistance of each ECM controlled relay and solenoid coil. Refer to ECM QDR Check under COMPUTERIZED ENGINE CONTROLS.

See ECM wiring diagram for coil terminal identification of solenoid(s) and relay(s) to be checked. Replace any relay or solenoid if the coil resistance measures less than 20 ohms.