Vacuum Diaphragm With PCM (Automatic or Manual Transmission)
DTC 32 AT W/O Tier 1 (PCM):
EGR Circuit (PCM):
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.
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 02S 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 then 2% change in throttle.
- Above 32 mph "Closed Loop" operation.
- Max short term fuel trim less then 6 counts for 3.2 seconds.
- Desired EGR command greater then then 93%.
- MAP above 47.5 kPa or less then 15 kPa.
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 gage 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 cause 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 "PCM Wiring Diagram" for coil terminal ID of solenoid(s) and relay(s) to be checked.
Replace any solenoid where resistance measures less than 20 ohms,