Exhaust Gas Recirculation: Testing and Inspection

EGR System Check:

Wiring Diagram For EGR System Check:

EGR SYSTEM

CIRCUIT DESCRIPTION:

The ECM operates a solenoid to control the Exhaust Gas Recirculation Valve. This solenoid is normally closed. By providing a ground path, the ECM energizes the solenoid which allows vacuum to pass to the EGR valve. The ECM control of the EGR valve is based on the following inputs:

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

If Code 24 is stored, use that chart first.

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. Checks for solenoid stuck open.

2. Checks for solenoid always being energized.

3. Grounding test terminal should energize solenoid and vacuum should drop.

4. Negative backpressure valve should hold vacuum with engine "OFF."

5. When engine is started, exhaust backpressure should cause vacuum to bleed off and valve to fully close.


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.