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For 1990-2009 cars only

ABS Red Brake SVC And 4WD Light On HVAC Blower Inoperative - keywords B1375 C0379 DTC HI4 ignition IPC L04 MIL on U1000 U1041

Subject: ABS Red Brake SVC and 4WD Light On HVAC Blower Inoperative

Models:2004-2007 Buick Rainier
2002-2007 Chevrolet Trailblazer, Trailblazer EXT and Trailblazer SS
2002-2007 GMC Envoy, Envoy XL, Envoy XUV and Envoy Denali
2002-2004 Oldsmobile Bravada



This PI was superseded to update model years. Please discard PIT3832A.


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

Vehicle may exhibit a combination or all of the following symptoms: ABS light on, Red BRAKE light on, Service 4WD light on, HVAC blower motor inoperative. Various DTCs may also be present.

Recommendation/Instructions:

Diagnose for loss of battery voltage to the rear fuse block on circuit 300 ORN for the following fuses:

HVAC 30 A, 4WD 15 A, HVAC 1 10 A, BRAKE 10 A, TBC RUN 3 A.

  1. Check circuit 300 ORN for battery voltage when the ignition key is in the RUN position.
  2. Check for battery voltage at the rear fuse block under the rear seat Connector C1 pin D9.
  3. If battery voltage IS NOT present at these locations, check for voltage at the ignition switch pin G for circuit 300 ORN.
  4. If battery voltage IS present at the ignition switch pin G, check circuit 300 for an open.
  5. If battery voltage IS NOT present at the ignition switch pin G, replace the ignition switch.

Note: This PI does not apply to the Saab 97x. The 97x has a unique ignition switch location and an electrical harness. With this new switch, the electrical center pin designations and the ignition switch connector is different. In the event the concern above is experienced in a Saab 97x, circuit 300 can be checked for integrity using the appropriate schematics in eSI.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.