Chart C9, Fast Idle Solenoid Electrical Check
The fast idle solenoid is an ECM controlled and normally retracted (de-energized). It is extended (energized) on both 5.7L and 4.3L applications when engine coolant temperature is below 100.4°F (38°C) or above 216°F (120°C). It is also extended on 4.3L engines to maintain correct idle speed when the A/C clutch is engaged.
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- With engine at normal operating temperature and A/C off (4.3L) fast idle solenoid plunger should be retracted (de-energized).
- Disconnecting coolant temperature sensor simulates a cold engine. Fast idle solenoid should extend.
- Determines if solenoid malfunction is caused by open solenoid, open circuit, or ECM.
- Solenoid is extended when it should be retracted. This step checks for grounded circuit, grounded solenoid, or faulty ECM.