Idle Speed/Throttle Actuator - Electronic: Testing and Inspection

Fig. 7 ISC (Idle Speed Control) System.:

Fig. 54 Testing BAC valve. Turbo:

The ISC system, Fig. 7, consisting of the BAC valve and the control system, improves idle smoothness by controlling the intake air amount detected by the air flow meter by regulating the amount of bypass air that passes through the throttle body.

1. Disconnect BAC valve electrical connector.
2. Start engine and run at idle.
3. Pinch air hose and note engine speed. When engine is cold, engine speed should drop. When engine is warm, engine speed should remain unchanged.
4. Connect BAC valve electrical connector.
5. Warm engine to normal operating temperature and run at idle.
6. Ensure idle speed is within specification.
7. Disconnect BAC valve electrical connector and ensure engine speed decreases, then reconnect connector.

ISC VALVE RESISTANCE

1. Disconnect BAC valve electrical connector.
2. Connect ohmmeter to terminals of of BAC valve and ensure resistance is 5 - 20 ohms.