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Home >> Saturn >> 2000 >> LS2 Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0571: Cruise/Brake Switch Circuit >> Diagnostic Procedures
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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. After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Check BCM/ECM/CRUISE/ABS fuse (10-amp) and BRAKE fuse (10-amp). Fuses are located in underhood fuse/relay block. Replace blown fuse(s). After replacing fuse(s), or if fuses are okay, go to next step.
  3. Using scan tool, monitor brake switch and brake/cruise switch status while depressing and releasing brake pedal. If brake/cruise switch follows brake pedal command, but brake switch does not, go to next step. If brake switch follows brake pedal command, but brake/cruise switch does not, go to step  8. If both switches follows brake pedal command, problem is intermittent. See DIAGNOSTIC AIDS .
  4. Verify stoplight operation. If stoplights do not operate properly, go to next step. If stoplights operate properly, observe scan tool display when brakes are applied. If scan tool indicates ON, replace ECM. If scan tool indicates OFF, check for open in Light Blue wire between stoplight switch and ECM. Repair as necessary. If circuit is okay, check for terminal tightness at connectors. Repair as necessary. If terminals are okay, replace ECM.
  5. If stoplights are always on, check for short in Light Blue wire between stoplight switch and ECM. Repair as necessary. If circuit is okay, replace brake switch. If stoplights are always off, go to next step.
  6. Turn ignition off. Disconnect ECM harness connector J2. Turn ignition on, with engine off. Check stoplight operation while depressing brake pedal. If stoplights are working, replace ECM. If stoplights are not working, go to next step.
  7. Turn ignition off. Disconnect stoplight switch harness connector. Remove all stoplight bulbs. Check resistance between ground and stoplight switch harness connector terminal No. 2 (Light Blue wire). If resistance is less than 2 ohms, repair short to ground in Light Blue wire to fuse block. Replace fuse. If resistance is not less than 2 ohms, replace stoplight switch.
  8. Verify brake/cruise switch status on scan tool. If switch status reads ON, go to next step. If switch status reads OFF, disconnect brake/cruise switch harness connector. Monitor brake/cruise switch status on scan tool. If switch status reads ON, replace brake/cruise switch. If switch status reads OFF, repair short to voltage in Brown wire between brake/cruise switch and ECM.
  9. Disconnect brake/cruise switch harness connector. Connect a test light between ground and brake/cruise switch harness connector terminal No. 1 (Pink wire). If test light illuminates, go to next step. If test light does not illuminate, repair open in Pink wire between brake/cruise switch and underhood fuse/relay block.
  10. Connect test light between brake/cruise switch 2-pin harness connector terminals. Using scan tool, monitor brake/cruise switch status while depressing and releasing brake pedal. If test light is on, go to next step. If test light is off and brake/cruise switch reads OFF, check for terminal tightness at connectors. Repair as necessary. If terminals are okay, replace cruise switch. If test light is off and brake/cruise switch reads ON, go to step  12.
  11. Check for short to ground in Brown wire between cruise switch and ECM. Repair as necessary. If circuit is okay, replace ECM.
  12. Check for open in Brown wire between cruise switch and ECM. Repair as necessary. If circuit is okay, check for terminal tightness at connectors. Repair as necessary. If terminals are okay, replace ECM.

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