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Rear Window Defogger Indicator Malfunction

  1. Ignition OFF, disconnect the X2 harness connector at the HVAC control module.
  2. Disconnect the RR DEFOG relay.
  3. Connect a test lamp between the control circuit terminal 86 and ground.
  4. Ignition ON, command the Rear Defog Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the HVAC control module.
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