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Test B: Horns Inoperative

  1. If horns diagnostic system check has been performed, go to next step. If horns diagnostic system check has not been performed, go to HORNS DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Press horn switch on steering wheel. If horns operate normally, go to next step. If horns do not operate normally, go to step  5 .
  3. Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). DLC is located under left side of instrument panel. Turn ignition switch to RUN position. Using scan tool, command Body Control Module (BCM) horn output On and Off. If horns do not sound continuously, go to next step. If horns sound continuously, horn concern may be intermittent. See PRELIMINARY INSPECTION  under TROUBLE SHOOTING.
  4. Check for open or high resistance in Black wire between BCM harness connector C1 terminal A11 and underhood junction block harness connector C3 terminal A8. See Figure and Figure . If problem is found, repair as necessary and go to step  21 . If no problem is found, go to step  11 .
  5. Turn ignition switch to OFF position. Remove horn relay from underhood junction block. Underhood junction block is located at right front of engine compartment, above battery. See Figure . Using test light connected to ground, probe horn relay coil voltage supply socket (circuit No. 740). See Figure . See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step  14 .
  6. Connect test light between horn relay coil voltage supply (circuit No. 740) and horn relay control circuit (circuit No. 28). See Figure . See WIRING DIAGRAMS  . Press and hold horn switch. If test light illuminates, go to next step. If test light does not illuminate, go to step  15 .
  7. Using test light connected to ground, probe horn relay switch voltage circuit (circuit No. 740). See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step  16 .
  8. Momentarily connect a fused (15 amp) jumper wire between horn relay switch voltage circuit (circuit No. 740) and horn control circuit (circuit No. 29). See WIRING DIAGRAMS  . If horns do not sound, go to next step. If horns sound, go to step  12 .
  9. Reconnect horn relay. Disconnect either horn assembly 2-pin harness connector. Horn assemblies are located on front bumper impact bar, below right and left headlights. Using a test light connected to ground, probe horn assembly harness connector terminal "B" (Dark Green wire). Press horn switch on steering wheel. If test light illuminates, go to next step. If test light does not illuminate, go to step  17 .
  10. Connect test light between horn assembly harness connector terminals "A" (Black wire) and "B" (Dark Green wire). Press and hold horn switch. If test light illuminates, go to next step. If test light does not illuminate, go to step  18 .
  11. Check for poor, loose or corroded terminals at BCM harness connectors. If problem is found, repair as necessary and go to step  21 . If no problem is found, go to step  19 .
  12. Check for poor, loose or corroded terminals in horn relay socket connector. If problem is found, repair as necessary and go to step  21 . If no problem is found, go to step  20 .
    13. NOTE: A resistance as low as 0.5 ohms could cause operating problems with horns. Although unlikely, it is possible that both horns are defective.
  13. Repair high resistance in Dark Green wires between underhood junction block harness connector C2 terminal A4 and both horn assembly harness connector terminals "B". See Figure . Repair high resistance in Black wire between ground and both horn assembly harness connector terminals "A". Ground points are located on top of front upper crossmember, at appropriate side. See WIRING DIAGRAMS  . After repairs are made, go to step  21 .
  14. Repair open or high resistance in horn relay coil voltage circuit between underhood fuse block HORN fuse and horn relay socket cavity (circuit No. 740). See Figure . See WIRING DIAGRAMS  . After repairs are made, go to step  21 .
  15. Disable air bag system. See appropriate AIR BAG RESTRAINT SYSTEMS article. Repair open or short to voltage in horn relay control circuit. Horn relay control circuit includes horn slip ring and horn switch. See WIRING DIAGRAMS  . After repairs are made, enable air bag and go to step  21 .
  16. Repair open or high resistance in battery voltage circuit of horn relay switch (circuit No. 740). See Figure . See WIRING DIAGRAMS  . After repairs are made, go to step  21 .
  17. Repair open or high resistance in horn control circuit between horn relay socket cavity (circuit No. 29) and horn assembly harness connector "B" (Dark Green wire). See Figure . See WIRING DIAGRAMS  . After repairs are made, go to step  21 .
  18. Repair open or high resistance in Black wire between ground and horn assembly harness connector terminals "A". Ground points are located on top of front upper crossmember, at appropriate side. See WIRING DIAGRAMS  . After repairs are made, go to step  21 .
  19. Replace BCM. See BODY CONTROL MODULES - AZTEK article. After repairs are made, go to step  21 .
  20. Replace horn relay. After repairs are made, go to next step.
  21. Operate horns. If horn operates normally, testing is complete. If horns do not operate normally, go to step  1 .
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