Idle/Throttle Speed Control Unit: Testing and Inspection

Chart C-2:

Idle Speed Control Circuit:

CIRCUIT DESCRIPTION:

The ECM controls a solenoid to regulate an opening at the throttle body. The amount of the opening determines the idle speed. The ISC is regulated according to engine load. A stalling condition or rough idle could be caused by the ISC valve not functioning properly.

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

1. This checks if B+ is present at solenoid.

2. This checks if the ECM is supplying a ground path.

3. This checks the resistance of the ISC solenoid. Should be 11-14 ohms at 20°C (68°F).