Code 32 - EGR Vacuum Control Circuit: Notes

The EGR valve is opened by engine vacuum. In order to control and monitor EGR application an Electronic Vacuum Regulator Valve (EVRV) is used. The EVRV is composed of 2 devices: EGR solenoid (normally closed) and EGR vacuum switch (normally open).

The EGR vacuum is controlled when the ECM grounds circuit No. 435, energizing the EGR solenoid. ECM controls pulse width modulation by varying the vacuum source "on" time, as compared to "off" time. This is done thousands of times a second.

The EGR is monitored by the ECM through the EGR vacuum switch. The EGR vacuum switch (a normally open electrical switch) has an orifice which restricts the vacuum signal to the EGR vacuum switch. When sufficient vacuum reaches the EGR vacuum switch, the electrical switch closes. There should also be sufficient vacuum to open the EGR valve.

Code 32 will set if the vacuum switch closes at idle or does not close when engine is under a load (less than wide open throttle).

1. The "Scan" tester displays the condition of the EGR diagnostic switch. In Park or Neutral, the display should read "NO" or "OFF" (open switch).
2. Under moderate engine load, the display will switch from "NO" or "OFF" to "YES" or "ON".
3. This test checks the integrity of the 12-volt feed and ground circuits. If these circuits check okay, the fault is elsewhere in the EVRV/EGR control circuit.
4. A test light connected between terminals "A" and "B" will verify the integrity of the ECM wiring and check for proper ECM operation.
5. If the "Scan" tester displays "YES" or "ON" at engine idle, disconnect the EVRV harness. If display remains unchanged, the fault is either a short to ground in circuit No. 932 or the ECM.
6. If the EGR display switches from "YES" or "ON" to "NO" or "OFF" when the EVRV is disconnected, the fault is either in the EVRV/EGR solenoid, circuit No. 435 or the ECM. Probing at terminal "B" will further isolate the fault. If the test light is on, disconnect ECM "A" and "B" connector before checking circuit No. 435 for a short to ground since the short could be inside the ECM.