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Home >> GMC >> 1999 >> Jimmy 4D Utility, 4WD >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> Body Control Modules >> Diagnostic Tests >> DTC B2585: Park Light Control Circuit Malfunction >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform BCM diagnostic system check. See BCM DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS. After performing system check, go to next step.
  2. Turn headlight switch to AUTO/OFF position. Using scan tool, ensure vehicle is in LIGHT state when performing tests. Ensure parking brake is released. Using a dark tape, cover ambient light sensor. See COMPONENT LOCATIONS  . Turn ignition on. If instrument panel lights illuminate, go to step 5). If instrument panel lights do not illuminate, go to next step.
  3. Turn ignition off. Check PARK LPS fuse (20-amp), located in Underhood Bussed Electrical Center (UBEC). If fuse is okay, go to next step. If fuse is open, go to step 12).
  4. Check PARK LP fuse (10-amp), located in instrument panel fuse block. If fuse is okay, go to next step. If fuse is open, go to step 16).
  5. Turn ignition off. Disconnect Light Blue 24-pin BCM connector. Remove park light relay from Body Bussed Electrical Center (BBEC). Using DVOM, measure resistance of White wire between BBEC cavity F6 and Light Blue BCM connector terminal A5. See WIRING DIAGRAMS  . See Figure . If 0-5 ohms exists, go to next step. If 0-5 ohms does not exist, go to step 20).
  6. Using DVOM, measure resistance of park light relay between terminals No. 1 and 2. If 0-95 ohms exists, go to next step. If 0-95 ohms does not exist, go to step 21).
  7. Remove PARK LP fuse (10-amp) from instrument panel fuse block. Using DVOM, measure resistance of Light Blue wire between BBEC cavity E6 and PARK LP fuse terminal K8 at instrument panel fuse block. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, go to step 22).
  8. Using a fused jumper wire, connect park light relay terminal No. 2 to battery voltage and terminal No. 1 to ground. Using DVOM, measure resistance of park light relay between terminals No. 3 and 5. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, go to step 21).
  9. Ensure Light Blue BCM connector is disconnected. Using DVOM, measure resistance of Brown wire between PARK LPS fuse terminal L7 and Light Blue BCM connector terminal B6. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, go to step 24).
  10. Install PARK LP fuse (10-amp) into instrument panel fuse block. Reconnect all components. Clear DTCs. Turn ignition off for 10 seconds. Turn ignition on. Check for DTCs. If DTC B2585 is set as a current code, go to next step. If DTC B2585 is not set as current code, DTC is intermittent. See DIAGNOSTIC AIDS.
  11. Replace BCM. See BODY CONTROL MODULE (BCM)  under REMOVAL & INSTALLATION. Program BCM and perform relearn procedure. See PROGRAMMING  . After programming module, go to step 25).
  12. Replace PARK LPS fuse (20-amp) in UBEC. Turn ignition on and recheck condition of PARK LPS fuse. If PARK LPS fuse blows, go to step 15). If PARK LPS fuse does not blow, go to next step.
  13. Clear DTCs. Turn ignition off for 10 seconds. Turn ignition on. Check for DTCs. If DTC B2585 is set as a current code, go to next step. If DTC B2585 is not set as current code, go to step 25).
  14. Remove tape covering ambient light sensor, then go to step 4).
  15. Repair short to ground in Orange wire to PARK LPS fuse in UBEC. See WIRING DIAGRAMS  . After repairs, go to step 25).
  16. Replace PARK LP fuse (10-amp) in instrument panel fuse block. Remove tape covering ambient light sensor. Turn ignition on and recheck condition of PARK LP fuse. If PARK LP fuse blows, go to step 18). If PARK LP fuse does not blow, go to next step.
  17. Cover ambient light sensor with dark tape. Check PARK LP fuse. If PARK LP fuse blows, go to step 19). If PARK LP fuse does not blow, go to step 25).
  18. Repair short to ground in Brown wire to PARK LP fuse in instrument panel fuse block. After repairs, go to step 25).
  19. Check for short to ground in Light Blue wire between BBEC and instrument panel fuse block. Repair as necessary and go to step 25). If Light Blue wire is okay, go to next step.
  20. Check for open in White wire between BCM and BBEC. Repair as necessary. After repairs, go to step 25). If White wire is okay, go to step 24).
  21. Replace park light relay. After replacing relay, go to step 25).
  22. Repair open in Light Blue wire between BBEC and instrument panel fuse block. After repairs, go to step 25).
  23. Replace BBEC. After replacing BBEC, go to step 25).
  24. Repair open in Brown wire between BCM and instrument panel fuse block. After repairs, go to next step.
  25. Clear DTCs. After clearing DTCs, perform BCM diagnostic system check. See BCM DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS.
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