Powertrain Controls - ECM/PCM

Code 32 Chart:

Code 32 Wiring Diagram:

***UPDATED BY CHEVROLET TSB 91-327-6E DATED MAY 1991

CIRCUIT DESCRIPTION:

The Exhaust Gas Recirculation (EGR) valve vacuum is controlled by an Electronic Control Module (ECM) controlled solenoid. The ECM will turn the EGR "ON" and "OFF" (Duty Cycle) by grounding CKT 435. The duty cycle is calculated by the ECM based on information from the coolant temperature, air flow and engine rpm. There should be (NO EGR) when in park or neutral, Throttle Position Sensor (TPS) input below a specified value, or TPS indicating Wide Open Throttle (WOT), or the MAT sensor below 15~C (59~F). With the ignition "ON," engine stopped, the EGR solenoid is de-energized and by grounding the diagnostic terminal, the solenoid is energized.

The ECM will check EGR operation when:

- Vehicle speed is above 30 mph
- MAP is as listed in table below
- TPS is between 5% and 30%
- No more than 0.4% change in TPS

Map Sensor Operating Range:

NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.

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

1. By grounding the diagnostic test terminal, the EGR solenoid should close and hold vacuum. The vacuum may bleed off slowly, but this is not considered a fault.

2. This test will determine if the electrical control part of the system is at fault, or if the connector or solenoid are at fault.


3. By plugging the EGR valve side and ungrounding the diagnostic terminal, the solenoid valve should open and allow vacuum to bleed off through the vent

4. With the engine not running and vacuum applied to the valve, the valve should move to the fully open position.

5. Due to this engine using a negative back pressure valve, the valve should close when the engine is cranked over.

DIAGNOSTIC AIDS:

The ECM monitors integrator during a Code 32 test and must detect a change to pass the test. If a integrator is fixed to lean or fixed to rich when a Code 32 test is run, a Code 32 may set. Repair the problem which resulted in a fixed integrator. The EGR circuit can be inoperative if the P/N switch is mis-adjusted or faulty. The EGR is disabled when in park or neutral. To check the P/N switch refer to CHART C-1A.

Suction from the shop exhaust hoses can alter backpressure and may affect the the function of the EGR valve during in-stall testing.

Thoroughly check that the EGR vacuum harness is not plugged or restricted. If the vacuum harness is pushed on the solenoid to far, it may plug the end of the vacuum line and cause a Code 32. Make sure the vacuum lines are at the right locations of the EGR solenoid. The vacuum source goes to the orifice side of the EGR solenoid.