With 4L80-E Automatic Transmission

Exhaust Gas Recirculation (EGR) Circuit Check:

Exhaust Gas Recirculation (EGR) Circuit:

Circuit Description:
The PCM operates an EVRV solenoid to control the Exhaust Gas Recirculation (EGR) valve. This EVRV solenoid is normally closed. By providing a ground path, the PCM energizes the EVRV solenoid which then allows vacuum to pass the EGR valve.

The PCM monitors EGR effectiveness by de-energizing the EVRV solenoid, thereby, shutting off vacuum to the EGR valve diaphragm. With the EGR valve closed and O2 sensor fluctuating normally, fuel integrator counts will be greater than they were during normal EGR operation. If the change is not within the calibrated window, a Code 32 will be set.

The PCM will check EGR operation when:

^ Engine speed is greater than 1600 rpm

^ Engine vacuum is between 20 and 60 kPa (6" and 18" Hg)

^ No change in throttle position while test is being performed

Test Description:
Numbers below refer to circled numbers on the diagnostic chart.

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

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

3. The vehicle must be driven during this test in order 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 PCM is commanding the system "ON".

Diagnostic Aids:
Before replacing PCM, use ohmmeter and check resistance of each PCM controlled relay and solenoid coil.

Refer to "PCM Wiring Diagram" for coil terminal identification of solenoids and relays to be checked. Replace any relay or solenoid if the coil resistance measures less than 20 ohms.