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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1811 (Fixed And MOVEABLE Windows) >> Diagnostic Information and Procedures >> DTC B0285 or B0286 >> Circuit/System Testing >> Rear Defog Indicator Malfunction

Rear Defog Indicator Malfunction

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector C1 at the HVAC control module.
  2. Ignition OFF, test for less than 1 ohm of resistance between the ground circuit terminal 12 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Disconnect the REAR DEFOG relay.
  4. Connect a test lamp between the control circuit terminal 24 and ground.
  5. 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 command 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.
  6. If all circuits test normal, test or replace the HVAC control module.
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