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DTC B2575: ALC Headlight System Fault: Testing

  1. If Body Control Module (BCM) diagnostic system check has been performed, go to next step. If Body Control Module (BCM) diagnostic system check has not been performed, go to BODY CONTROL MODULE (BCM) DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS.
  2. Connect scan tool to Data Link Connector (DLC), located to left of steering column. Turn ignition on. Using scan tool, command ALC headlight relay ON and OFF. If relay does not turn on and off (click), go to next step. If relay turns on and off (clicks), go to DIAGNOSTIC AIDS  .
  3. Turn ignition off. Remove ALC relay from underhood junction block. Turn ignition on. Using a test light connected to ground, probe relay cavity terminal No. 85. If test light illuminates, go to next step. If test light does not illuminate, go to step  10 .
  4. Connect a test light between relay cavity terminals No. 86 and No. 85. Using scan tool, command ALC relay ON and OFF. If test light does not turn on and off, go to next step. If test light turns on and off, go to step  8 .
  5. If test light stays off, go to next step. If test light stays on, go to step  7 .
  6. Check for open on Pink/White wire between underhood junction block connector C3 terminal C11 and BCM connector C1 terminal A1. See Figure . If circuit is okay, go to step  9 . If circuit is open, repair as necessary. After repair, go to step  13 .
  7. Check for short to ground on Pink/White wire between underhood junction block connector C3 terminal C11 and BCM connector C1 terminal A1. If circuit is okay, go to step  9 . If circuit is shorted to ground, repair as necessary. After repair, go to step  13 .
  8. Check ALC relay and cavity terminals for damage and poor connections. If no problem is found, go to step  11 . If connections are poor, repair as necessary. After repair, go to step  13 .
  9. Check BCM and harness connector terminals for damage and poor connections. If no problem is found, go to step  12 . If connections are poor, repair as necessary. After repair, go to step  13 .
  10. Repair power feed circuit to ALC relay. See POWER DISTRIBUTION article in WIRING DIAGRAMS. After repair, go to step  13 .
  11. Replace ALC relay. Go to step  13 .
  12. Replace BCM. See BODY CONTROL MODULE (BCM)  under REMOVAL & INSTALLATION. Program BCM. See BODY CONTROL MODULE (BCM)  under PROGRAMMING. After repair, go to next step.
  13. Reconnect all disconnected components and connectors. Clear DTCs. Operate vehicle under conditions that set DTC. If DTC resets, go to step  2 . If DTC does not reset, system is okay.
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