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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G2500, VAN CARGO EXTENDED, 5.7 R, L31/KL8REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 9 (BODY CONTROL MODULES)DIAGNOSTIC TESTSDTC B1478: RETAINED ACCESSORY POWER CIRCUIT HIGHTESTING
2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8

DTC B1478: Retained Accessory Power Circuit High: Testing

2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8SECTION Testing
WARNING: This page is about a different car, the 2002 Chevrolet Monte Carlo, 2002 Chevrolet Impala, 2001 Chevrolet Monte Carlo, and 2001 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform Retained Accessory Power (RAP) system diagnostic system check. See RETAINED ACCESSORY POWER (RAP) SYSTEM DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. If Retained Accessory Power (RAP) system diagnostic system check has been performed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to RUN position. Using scan tool, command RAP relay ON and OFF. If RAP relay does not operate as commanded, go to next step. If RAP relay operates as commanded, check for intermittent problem. See DIAGNOSING INTERMITTENTS . Repair or replace as necessary and go to step  13.
  3. Turn ignition switch to OFF position. Remove RAP relay from left instrument panel fuse block. Turn ignition switch to RUN position. Connect a test light between ground and RAP relay connector terminal No. 707 in left instrument panel fuse block. See Figure. Using scan tool, command RAP relay ON and OFF. If test light turns on and off as commanded, go to next step. If test light does not turn on and off as commanded, go to step  5.
  4. Connect a test light between RAP relay connector terminals No. 707 and No. 1050 in left instrument panel fuse block. See Figure. Using scan tool, command RAP relay ON and OFF. If test light turns on and off as commanded, go to step  8. If test light does not turn on and off as commanded, go to step  10.
  5. If test light remains illuminated with both commands, go to step  7. If test light does not remain illuminated with both commands, go to next step.
  6. Check for open in circuit between RAP relay connector terminal No. 707 in left instrument panel fuse block and BCM Gray, 24-pin harness connector C2 terminal B9 (Black wire). See WIRING DIAGRAMS . Repair as necessary and go to step  13. If circuit is okay, go to step  9.
    Fig 1: Identifying Left/Right I/P Accessory Wiring Junction Block Harness Connector
    G00009286Courtesy of GENERAL MOTORS CORP.
  7. Check for short to power in circuit between RAP relay connector terminal No. 707 in left instrument panel fuse block and BCM Gray, 24-pin harness connector C2 terminal B9 (Black wire). See WIRING DIAGRAMS . Repair as necessary and go to step  13. If circuit is okay, go to step  9.
  8. Check for poor connection at RAP relay connector. Repair as necessary and go to step  13. If connection is okay, go to step  11.
  9. Check for poor connection at BCM Gray, 24-pin connector C2. Repair as necessary and go to step  13. If connection is okay, go to step  12.
  10. Repair open or high resistance in circuit between RAP relay connector terminal No. 1050 in left instrument panel fuse block and ground connector G201. See WIRING DIAGRAMS . Repair as necessary and go to step  13.
  11. Replace RAP relay and go to step  13.
  12. Replace and program BCM. See BODY CONTROL MODULE  under REMOVAL & INSTALLATION. See BODY CONTROL MODULE  under PROGRAMMING. After repair, go to next step.
  13. Using scan tool, clear DTCs. Operate vehicle within CODE ENABLE CRITERIA  conditions. Using scan tool, retrieve DTCs. If DTC B1478 resets, return to step  2. If DTC B1478 does not reset, system is okay.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.