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Home › Isuzu › 1998 › Hombre S, 4.3 X › Repair and Diagnosis › Body & Frame › Body, Cab Control Systems › Body Control Module › Diagnosis & Testing › BCM Diagnostic System Check › Diagnostic Procedures

Diagnostic Procedures

  1. Turn headlight switch to ON position. Check TBC fuse (10-amp) in underhood bussed electrical center. Replace fuse if necessary. Install scan tool. If scan tool turns on, go to next step. If scan tool does not turn on, go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 SERIAL DATA LINE  .
  2. Using scan tool, attempt to establish communication with BCM. If scan tool communicates with BCM, go to next step. If scan tool does not communicate with BCM, go to step 4).
  3. Using scan tool, check for BCM related DTCs. If any DTC exists, go to appropriate DTC test. If no DTCs exist, system is operating properly.
  4. Attempt to establish communication with other systems connected to same serial data line (VCM, IPC, HVAC, etc.). If scan tool communicates with other systems, go to next step. If scan tool does not communicate with other systems, go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 SERIAL DATA LINE  .
  5. Check TBC fuse (10-amp) in underhood bussed electrical center. If fuse is okay, go to next step. If fuse is blown, go to step 10).
  6. Using a test light connected to ground, probe both sides of TBC fuse (10-amp). See WIRING DIAGRAMS  . If test light does not come on at both sides of fuse, go to step 11). If test light comes on at both sides of fuse, go to next step.
    NOTE: Disconnect module harness connectors in specific order, or BCM/TBC related DTCs will set.
  7. Turn ignition switch to OFF position. Disconnect BCM harness connectors C1 (Brown), C2 (Light Blue) and C3 (Purple). Turn ignition switch to ON position. Using a test light connected to ground, backprobe BCM connector C1 terminal A2 (Orange wire). See WIRING DIAGRAMS  . If test light comes on, go to next step. If test light does not come on, go to step 13).
  8. Backprobe with self-powered test light between ground and BCM connector C1 terminals A1 and B1 (Black wires). If test light comes on at both circuits, go to step 14). If test light does not come on at both circuits, go to next step.
  9. Repair open in Black wire between BCM connector and ground. See WIRING DIAGRAMS  . After repair, go to step 18).
  10. Repair short to ground in Orange wire between BCM connector and underhood bussed electrical center. See WIRING DIAGRAMS  . After repair, go to step 18).
  11. Replace underhood bussed electrical center. After repair, go to step 18).
  12. Replace BCM. See BODY CONTROL MODULE (BCM)  under REMOVAL & INSTALLATION. Reconnect all disconnected components. Reprogram and relearn BCM. See BCM PROGRAMMING/RPO CONFIGURATION  and BCM RELEARN PROCEDURES under PROGRAMMING. If vehicle starts after repairs, repair is complete. If vehicle does not start after repairs, Perform reprogram and relearn procedures once more. If vehicle still will not start, go to appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES/SAFETY EQUIPMENT section.
  13. Repair open in Orange wire between BCM connector and underhood bussed electrical center. See WIRING DIAGRAMS  . After repair, go to step 18).
  14. Ensure ignition switch is in OFF position with BCM connectors disconnected. Turn ignition switch to ON position. Use test light and backprobe between ground and BCM connector C1 terminal B2 (Pink wire). See WIRING DIAGRAMS  . If test light comes on, go to step 16). If test light does not come on, go to next step.
  15. Repair open or short to ground in Pink wire between BCM and instrument panel fuse block. See WIRING DIAGRAMS  . Replace GAUGES fuse (10-amp) if necessary. After repairs, go to step 18).
  16. Ensure ignition switch is in OFF position with BCM connectors disconnected. Turn ignition switch to ON position. Use test light and backprobe between ground and BCM connector C1 terminal B9 (Brown wire). See WIRING DIAGRAMS  . If test light comes on, go to step 12). If test light does not come on, go to next step.
  17. Repair open or short to ground in Brown wire between BCM and instrument panel fuse block. See WIRING DIAGRAMS  . Replace CRUISE fuse (10-amp) if necessary. After repairs, go to next step.
  18. Turn ignition switch to OFF position. Reconnect all disconnected connectors to BCM. Clear DTCs with scan tool. If DTCs clear and do not come back, repair is complete. If DTCs are present, go to BCM DTC DEFINITION  table.
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