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Home >> Audi >> 1990 >> 200 Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Idle Control System >> Cis Digital Control >> Idle Speed Stabilization System
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Idle Speed Stabilization System

  1. Ensure engine temperature is less than 68°F (20°C). Disconnect harness connector at thermoswitch. Check continuity of idle stabilizer thermoswitch to ground.
  2. If continuity does not exist, replace idle stabilizer thermoswitch. If continuity exists, warm idle stabilizer thermoswitch to at least 104°F (40°C). Thermoswitch should now show an open circuit. If not, replace idle stabilizer thermoswitch.
  3. Warm engine to at least 176°F (80°C). Disconnect electrical harness for idle stabilizer valve. Connect a voltmeter across both terminals. Turn ignition on. Ensure battery voltage is present. If battery voltage is not present, go to step 5).
  4. If battery voltage is present, reconnect idle stabilizer valve. Touch idle stabilizer valve and check for vibrations. If vibration is not felt, replace idle stabilizer valve.
  5. Remove idle stabilizer control unit (located in relay panel). Turn ignition on and ensure 12 volts exist between terminals No. 14 (socket 11) and 5 (socket 12).
  6. If not, repair wiring. Turn A/C on. Ensure 12 volts exist between terminals No. 2 (socket 12) and 5 (socket 12). If not, check wiring from A/C relay pin No. 87M in relay panel.
  7. Check resistance between terminals No. 4 (socket 12) and 11 (socket 11) of idle stabilizer control unit. Ohmmeter should indicate 20-40 ohms. If not, check continuity of wiring between idle stabilizer valve and relay board.
  8. Ensure throttle switch is at idle position. Ensure 12 volts exist at terminal No. 8 (Gray wire) of idle stabilizer control unit. If not, check and adjust throttle switch or repair wiring. With 12 volts are present at idle, slightly open throttle. Ensure voltage drops to zero.
  9. Disconnect idle stabilizer thermoswitch harness lead. Ensure continuity exists between terminal No. 13 (socket 11) and thermoswitch lead (Blue/Green wire). If continuity does not exist, repair wiring. If all circuits of idle stabilizer system are okay and idle stabilizer valve still does not work, replace idle stabilizer control unit.
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