GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2009 🢒 TrailBlazer - 4WD 🢒 Power and Signal Distribution 🢒 Wiring Systems and Power Management 🢒 Retained Accessory Power Malfunction

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Retained Accessory Power (RAP) Supply Voltage Circuit

B1477, 1

1

2

--

  1. The sunroof will not operate.
  2. The sunroof will remains on past the timer limit after key out and will not turn off when a vehicle door is opened.

Circuit/System Description

The body control module (BCM) controls the sunroof motor operation through the retained accessory power (RAP) supply voltage circuit. When the ignition switch is in either the ACC or the ON position, the BCM provides battery voltage to the RAP supply voltage circuit. When the ignition switch turns from ON or ACC to OFF, with all of the vehicle doors closed, the BCM still provides battery voltage to the circuit for 10 minutes, or until any vehicle door opens.

    • Ignition switch is in ACC or ON.
    • The vehicle was remote started.
    • The vehicle is in RAP mode.

Diagnostic Aids
    • A short to voltage on the retained accessory power (RAP) supply voltage circuit would cause DTC B1477 to set, and an inoperative sunroof.
    • An open/high resistance in the retained accessory power (RAP) supply voltage circuit will cause an inoperative sunroof.
    • A short to voltage on the retained accessory power (RAP) supply voltage circuit would cause the RAP function to remain on past the designated time.

Reference Information

Schematic Reference

Power Moding Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Retained Accessory Power (RAP) Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for Scan Tool Information

Circuit/System Verification

Important: Battery voltage must remain above 9.6 V for RAP to operate properly.

  1. With a scan tool, verify that BCM DTC B1477 is not set.
    2. ⇒If DTC B1477 is current, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

    Important: Verify that the interior lamps defeat switch is not activated.

  2. Observe the courtesy lamps while opening and closing the vehicle doors. The courtesy lamps should illuminate when the doors are opened and turn off approximately 30 seconds after closing.
    3. ⇒If the courtesy lamp operation is incorrect, refer to Courtesy Lamps Malfunction .

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector of the sunroof module.
  2. With the ignition key out of the ignition and the driver door open, verify a test lamp does not illuminate between the retained accessory power (RAP) supply voltage circuit terminal 3 of the sunroof module harness connector and ground.
    3. ⇒If the test lamp illuminates, test the ignition circuit for a short to voltage. If the circuit tests normal, test or replace the BCM
  3. Ignition ON and the test lamp still connected, verify the test lamp illuminates.
    4. ⇒If the test lamp does not illuminate, test the ignition circuit for a short open/high resistance. If the circuit tests normal, test or replace the BCM
  4. If the circuit tests normal, test or replace the sunroof motor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Sunroof Motor/Actuator Replacement
    •  Control Module References for BCM replacement, setup, and programming