Idle Up Control Valve: Testing and Inspection

Chart C-2C "Idle Load Compensator (ILC) Check:

Wiring Diagram - Idle Load Compensator (ILC) Check:

CHART C-2C

IDLE LOAD COMPENSATOR (ILC) CHECK


Circuit Description:

The Idle Load Compensator (ILC) is mounted on the carburetor and is used to control various low engine rpm conditions. The ILC uses a spring loaded vacuum sensitive diaphragm whose plunger extends when vacuum is not present. Vacuum to the ILC is controlled by the ECM through the ILC/RVB/EGR solenoid assembly. When the ECM turns "ON" the ILC solenoid assembly, vacuum is cut "OFF" to the ILC. Vacuum is regulated through the VRV and delayed under high load conditions (checked) by the DVDV and through the Anti-Diesel Solenoid (ADS). The ADS is energized when the IGN is turned "ON" allowing vacuum to the ILC and turned "OFF" when the IGN is "OFF." This supplies vacuum to the ILC keeping the plunger retracted so the engine can shut down without dieseling.


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

1. ILC plunger should be extended as no vacuum is being applied.

2. ILC plunger should retract if vacuum is applied.

3. Depressing the TPS should make the ECM turn the ILC quad-driver "ON," blocking vacuum to the ILC, simulating a WOT condition. Clear long term memory after this procedure as the ECM must relearn correct TPS voltage.


4. With test terminal grounded and TPS depressed, ECM should be turning "ON" ILC solenoid assembly. Test light should be "ON."

5. Anti-diesel solenoid is energized any time ignition is "ON" so test light should be "ON."

6. Test light should be "OFF" as ILC quad-driver should be turned "OFF".

7. If the test light goes out, the ECM has to be replaced as the quad-driver inside the ECM has failed.


**EMI