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Electronic Idle Speed Control: Testing

  1. Warm engine to normal operating temperature. Stop engine and disconnect plug from idle speed adjuster. Measure voltage across terminals in connector. If battery voltage is present, go to step  4).
  2. If no voltage is present, remove connector from control unit and measure voltage across terminals 2 (+) and 4 (-). If battery voltage is not present, check wiring and voltage supply relay. If battery voltage is present, check continuity of wiring from control unit to idle speed adjuster. Repair if required.
  3. Connect wiring harness to control unit and measure voltage at idle speed adjuster connector again. If no voltage is present, replace control unit.
  4. Connector at idle speed adjuster should be unplugged slightly so voltage readings can be measured while system is operating. Start engine and idle. Measure voltage across terminals at idle speed adjuster. If no voltage, replace control unit.
  5. If voltage measured was 4-6 volts, disconnect coolant temperature sensor and place jumper wires across connector terminals. Idle speed should increase to 750 RPM. If so, the system is okay. If not, go to next step.
  6. Disconnect idle speed adjuster. With engine running briefly apply battery voltage (using jumper wires) to idle speed adjuster terminals. If idle speed drops or engine stalls, replace control unit. If idle speed does not drop, replace idle speed adjuster.
    CAUTION: Do not apply battery voltage for more than 5 seconds to idle speed adjuster terminals.
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