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BCM Diagnostic System Check: Notes

NOTE: For wiring and connector terminal identification, see WIRING DIAGRAMS  .
NOTE: Use this check as the starting point for any Body Control Module (BCM) complaint. BCM is a very reliable component, and is not likely the cause of malfunction. Most malfunctions are caused by faulty wiring, connectors or components.
  1. Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. 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  3 .
  2. Using scan tool, check for BCM DTCs. If any DTC exists, go to appropriate DTC test. See BCM DTC DEFINITIONS  table under SELF-DIAGNOSTIC SYSTEM. If no DTCs exist, go to step  14 .
  3. Attempt to establish communication with other systems connected to same serial data line (PCM, RFA, 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  .
  4. Check V1 fuse (20-amp) located in power distribution fuse block. If fuse is blown, go to step  9 . If fuse is okay, go to next step.
  5. Turn ignition off. Disconnect BCM 24-pin connector C1. Using DVOM, measure voltage between BCM connector C1 terminal B3 (Red wire) and ground. See WIRING DIAGRAMS  . See Figure . If 10-13 volts is indicated, go to next step. If 10-13 volts is not indicated, go to step  11 .
  6. Turn ignition off. Disconnect BCM 32-pin connector C2. Using DVOM, measure resistance between BCM connector C2 terminal C1 (Black wire) and ground. If reading is 0-5 ohms, go to next step. If reading is greater than 5 ohms, go to step  12 .
  7. Using DVOM, check for continuity between BCM 24-pin harness connector C1, terminal B9 (Brown/White wire) and Data Link Connector (DLC) terminal No. 2 (Brown/White wire). If continuity exists, go to next step. If continuity does not exist, go to step  10 .
  8. Replace BCM. See BODY CONTROL MODULE (BCM)  under REMOVAL & INSTALLATION. Reprogram BCM. See PROGRAMMING  . Go to step  13 .
  9. Repair short to ground in Red wire between BCM and power distribution fuse block. Go to step  13 .
  10. Locate and repair open in Brown/White wire between BCM connector C1 and DLC terminal No. 2. Go to step  13 .
  11. Locate and repair open in BCM power circuit. Go to step  13 .
  12. Locate and repair open in BCM ground circuit. Go to next step.
  13. Turn ignition off. Reinstall all components or connectors. Install scan tool to DLC. Attempt to establish communication with BCM. If scan tool communicates with BCM, go to step  2 . If scan tool does not communicate with BCM, go to step  3 .
  14. Check operation of power door locks by pressing the LOCK/UNLOCK button. If power door locks operate, go to next step. If power door locks do not operate, repair as necessary. See appropriate wiring diagram in POWER DOOR LOCKS & REMOTE KEYLESS ENTRY SYSTEMS article.
  15. Check operation of power trunk release by pressing the trunk release button. If power trunk release operates, go to next step. If power trunk release does not operate, repair as necessary.
  16. Check operation of power fuel door release by pressing the fuel door release button. If power fuel door operates, go to next step. If power fuel door does not operate, repair as necessary.
  17. Turn ignition on. Ensure twilight sentinel feature is turned off and indicator light in OFF button will be on. Depress brake pedal and shift transmission to Drive. DRLs should come on. Shift transmission into Park. Rotate headlight switch to turn on parking lights. Rotate headlight switch to turn on low beam headlights. Push turn signal lever away from steering wheel to turn on high beams. Pull turn signal switch toward steering wheel to activate flash-to-pass feature of headlights. Turn headlights off. If headlights operate as specified, go to next step. If headlights do not operate as specified, repair as necessary. See appropriate wiring diagram in HEADLIGHT SYSTEMS & DAYTIME RUNNING LIGHTS article.
  18. Activate twilight sentinel by pressing and releasing the OFF button. OFF button indicator light will turn off. Rotate control dial to the top. Cover light sensor located on instrument panel. Low beams and parking lights should turn on. If twilight sentinel operates as specified, go to next step. If twilight sentinel does not operate as specified, see appropriate HEADLIGHTS - AUTOMATIC TWILIGHT SENTINEL article.
  19. Turn ignition off. Remove keys from ignition switch and exit vehicle. Ensure all doors are closed. Operate Remote Keyless entry (RKE) transmitter to lock and unlock doors, open trunk and fuel filler door. If RKE operates as specified, system is okay. If RKE does not operate as specified, repair as necessary. See appropriate wiring diagram in POWER DOOR LOCKS & REMOTE KEYLESS ENTRY SYSTEMS article.
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