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Home >> Buick >> 2001 >> Century Limited >> Repair and Diagnosis (Single Page) >> Body & Frame >> Ignition Switch/Steering Lock >> Steering Column & Steering Column Switches >> Symptom Tests >> Test B: Horns Inoperative >> Century & Regal

Century & Regal

  1. If horns diagnostic system check was performed, go to next step. If horns diagnostic system check was not performed, see HORNS DIAGNOSTIC SYSTEM CHECK (CENTURY & REGAL)  under SELF-DIAGNOSTIC SYSTEM.
  2. Press horn switch. If horns operate, go to next step. If horns do not operate, go to step  5 .
  3. Connect scan tool to Data Link Connector (DLC). DLC is located below left side of instrument panel, to right of steering column. Turn ignition switch to RUN position. Using scan tool, command horn relay ON and OFF. If horns do not operate with scan tool, go to next step. If horns operate with scan tool commands, check for intermittent or poor connections. Repair as necessary.
  4. Check for open or high resistance in Black wire between BCM harness connector C3 terminal A5 and underhood fuse block harness connector C2 terminal F7. See Figure and Fig 1 . If Black wire is okay, go to step  13 . If Black wire is not okay, repair as necessary. After repair, go to step  24 .
    Fig 1: Identifying Underhood Fuse Block Connector C3 Terminals
    G00010143Courtesy of GENERAL MOTORS CORP.
  5. Turn ignition switch to OFF position. Remove horn relay from underhood fuse block, located on right side of engine compartment, mounted to strut tower. Connect a test light between ground and horn relay cavity No. 85 (coil power supply circuit). If test light illuminates, go to next step. If test light does not illuminate, go to step  16 .
  6. Connect test light between horn relay cavities No. 85 (coil power supply circuit) and horn relay cavity No. 86 (relay control circuit). If test light illuminates, go to next step. If test light does not illuminate, go to step  17 .
  7. Connect test light between ground and horn relay cavity No. 85 (coil power supply circuit). If test light illuminates, go to next step. If test light does not illuminate, go to step  18 .
  8. Momentarily connect a fused (15-amp) jumper wire between horn relay cavity No. 85 (coil power supply circuit) and horn relay cavity No. 87 (horn control circuit). If horns do not operate, go to next step. If horns operate, go to step  14 .
  9. Install horn relay. Disconnect horn connector. Connect a test light between ground and horn connector Dark Green wire terminal. Press and hold horn switch. If test light illuminates, go to next step. If test light does not illuminate, go to step  19 .
  10. Connect test light between horn harness connector Dark Green and Black wire terminals. Press and hold horn switch. If test light illuminates, go to next step. If test light does not illuminate, go to step  20 .
  11. Check horn connector for intermittent or poor terminal contact. If terminal contact is okay, go to next step. If terminal contact is not okay, repair as necessary. After repair, go to step  24 .
  12. Connect a fused (15-amp) jumper wire between positive battery terminal and horn harness connector Dark Green wire terminal. Connect a second fused (15-amp) jumper wire between negative battery terminal and horn harness connector Black wire terminal. If horn does not operate, go to step  15 . If horn operates, go to step  23 .
  13. Check BCM connectors for intermittent or poor terminal contact. If terminal contact is okay, go to step  21 . If terminal contact is not okay, repair as necessary. After repair, go to step  24 .
  14. Check horn relay connector for intermittent or poor terminal contact. If terminal contact is okay, go to step  22 . If terminal contact is not okay, repair as necessary. After repair, go to step  24 .
    15. NOTE: Resistance of 0.5 ohms can cause operating problems with the horns.
  15. Repair high resistance in horn control circuit (Dark Green wire) or horn ground circuit (Black wire). After repair, go to step  24 .
  16. Repair open or high resistance in horn relay battery positive voltage circuit. After repair, go to step  24 .
    17. CAUTION: Horn switch is part of inflatable restraint steering wheel module. Disable air bag system. See SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in appropriate AIR BAG RESTRAINT SYSTEMS article.
  17. Repair open or short to voltage in horn relay control circuit between horn switch, slip ring, horn relay and BCM. After repair, go to step  24 .
  18. Repair open or high resistance in horn relay battery positive voltage circuit. After repair, go to step  24 .
  19. Repair open or high resistance in horn control circuit (Dark Green wire) between horn relay and horn assemblies. After repair, go to step  24 .
  20. Repair open or high resistance in horn ground circuit (Black wire) between horn assemblies and ground. Ground point is located at front left side of radiator support. After repair, go to step  24 .
  21. Replace BCM. Program as necessary. See BODY CONTROL MODULES - CENTURY & REGAL article. After repair, go to step  24 .
  22. Replace horn relay. After repair, go to step  24 .
  23. Replace horn assemblies. After repair, go to step  24 .
  24. Operate horn system to verify fault no longer exists. If fault still exists, go to step  1 .
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