Disconnect the idle speed sensor connector. Connect an ohmmeter to pin 4 of the sensor connector and ground. The resistance should be 0 ohms, then open the throttle slightly and the resistance should change to a value of ∞.
Check supply voltage. Connect a voltmeter between track 4 of the harness connector and ground (e.g. engine block). Turn on the ignition. Required value >4 V. Switch off the ignition.
Connector pinout differences:
- engine 1.5 l, release from 9.88 to 4.89: power = pin 3.
- 16 valve engine: power = pin 1.