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Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
  2. Using scan tool, monitor stop/brakelight switch. If scan tool display indicates RELEASED go to next step. If scan tool display does not indicate RELEASED, go to step  7.
  3. Depress brake pedal about halfway. If scan tool display indicates APPLIED, see DIAGNOSTIC AIDS . If scan tool display does not indicate APPLIED, go to next step.
  4. Check brakelight switch adjustment. Adjust as necessary. After adjusting switch, go to step  20. If no adjustment was necessary, go to next step.
  5. Check stop/brakelight fuse. If fuse is blown, go to step  8. If fuse is okay, go to next step.
  6. Disconnect stop/brakelight switch harness connector. Using a DVOM, check voltage between ground and stop/brakelight feed circuit at harness connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step  12.
  7. Turn ignition off. Disconnect TAC module and brakelight switch harness connectors. Check continuity of brakelight switch signal circuit. If continuity exists, go to step  10. If continuity does not exist, go to step  13.
  8. Disconnect brakelight switch harness connector. Using a test light connected to ground, probe brakelight switch feed circuit at harness connector. If test light illuminates, go to step  14. If test light does not illuminate, go to next step.
  9. Connect test light to battery voltage and probe brakelight switch signal circuit at harness connector. If test light illuminates, go to step  15. If test light does not illuminate, go to next step.
  10. Connect test light to ground and probe brakelight switch signal circuit at TAC module harness connector. If test light illuminates, go to step  16. If test light does not illuminate, go to next step.
  11. Remove brakelight switch. Check continuity across switch terminals while toggling switch by hand. If switch toggles from open to continuity, go to step  18. If switch does not toggle from open to continuity, go to step  17.
  12. Repair open in brakelight switch feed circuit. After repairs, go to step  20.
  13. Repair open in brakelight switch signal circuit. After repairs, go to step  20.
  14. Repair short to ground in brakelight switch feed circuit. After repairs, go to step  20.
  15. Repair short to ground in brakelight switch signal circuit. After repairs, go to step  20.
  16. Repair short to voltage in brakelight switch signal circuit. After repairs, go to step  20.
  17. Replace stop/brakelight switch. After replacing switch, go to step  20.
  18. Check for poor connections at brakelight switch and TAC module connectors. Repair as necessary. After repairs, go to step  20. If connections are okay, go to next step.
  19. Replace TAC module. After replacing module, go to next step.
  20. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step  2.
  21. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test.
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