Negative Backpressure EGR Valve

DTC 32 Chart (Backpressure):

EGR Circuit:

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

DTC 32 WILL SET WHEN
The PCM monitors EGR effectiveness by de-energizing the EGR control solenoid, thereby, shutting "OFF" vacuum to the EGR valve diaphragm. With the EGR valve closed, and O2S fluctuating normally, fuel integrator counts will be greater than they were during normal EGR operation. If the change is not within the calibrated window, after failing the test twice a DTC 32 will be set.

The PCM will check EGR operation when:
- Throttle position between 10% and 25% angle.
- Steady throttle with no more than 2% change in throttle.
- Above 32 mph "Closed Loop" operation.
- Max short term fuel trim less than 6 counts for 3.2 seconds.
- Desired EGR command greater than 93%.
- MAP above 15 kPa or less than 47.5 kPa.

ACTION TAKEN (PCM WILL DEFAULT TO)
The Malfunction Indicator Lamp (MIL) will illuminate.

DTC 32 WILL CLEAR WHEN
Conditions for fault are no longer present and Tech 1 "clear DTCs" function is used or 50 ignition switch keycycles have passed with no further faults or ignition switch is turned "OFF" and battery feed voltage is removed for 10 seconds.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. By commanding the EGR solenoid "ON," vacuum is applied to the EGR valve and the vacuum should hold.
2. When the diagnostic terminal is ungrounded, the vacuum to the EGR valve should bleed off through a vent in the solenoid and the valve should close. The gauge may or may not bleed off but this does not indicate a problem.
3. This test will determine if the electrical control part of the system is at fault, or if the connector or solenoid is at fault.
4. This system uses a negative backpressure valve which should hold vacuum with engine "OFF."
5. When engine is started, exhaust backpressure should causes vacuum to bleed off and valve should fully close.

DIAGNOSTIC AIDS
Before replacing PCM, use an ohmmeter and check the resistance of each PCM controlled relay and solenoid coil.

Refer to Engine Control Module / Diagrams / Electrical / ECM/PCM Wiring Diagrams for coil terminal ID of solenoid(s) and relay(s) to be checked.

Replace any solenoid where resistance measures less than 20 ohms.