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Home >> GMC >> 2000 >> C3500 HD 6.5 F, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - Diesel >> Diagnostic Tests >> DTC P0568: Cruise Set Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, see ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Connect scan tool. Turn ignition on. Turn cruise switch off. If scan tool indicates set switch is on, go to next step. If scan tool does not indicate set switch is on, go to step  4.
  3. Turn ignition off. Disconnect 24-pin PCM harness connector (Brown). Turn ignition on. Using test light connected to ground, probe set switch signal circuit at PCM harness connector. If test light illuminates, go to step  5. If test light does not illuminate, go to step  6.
  4. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS . If any additional DTCs are set, perform appropriate DTC test.
  5. Check for short to voltage in set switch signal circuit or set switch stuck in ON position. Repair as necessary. After repairs, go to step  8.
  6. Replace PCM. Perform PCM relearn procedures. See PROGRAMMING . After repairs, go to next step.
  7. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0568. Operate vehicle within the 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, go to step  2.
  8. Using scan tool, check for DTCs. If any undiagnosed DTCs are set, perform appropriate DTC test. If no DTCs are set, system is okay.
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