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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 P0126: Insufficient ECT For Stable Operation >> 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. Check for DTCs. If any engine coolant temperature DTCs are set, perform appropriate DTC test. If no engine coolant temperature DTCs are set, go to next step.
  3. Turn ignition on. Disconnect ECT sensor harness connector. Using scan tool, check ECT sensor value. If ECT sensor value is less than -31°F (-35°C), go to next step. If ECT sensor value is not less than -31°F (-35°C), perform diagnostic procedure for DTC P0117. See DTC P0117: ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT LOW VOLTAGE .
  4. Using jumper wire, jumper ECT sensor harness connector terminals. If scan tool indicates ECT value is greater than 302°F (150°C), go to next step. If ECT value is not greater than 302°F (150°C), perform diagnostic procedure for DTC P0118. See DTC P0118: ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT HIGH VOLTAGE .
  5. Reconnect ECT sensor harness connector. Start and warm engine to normal operating temperature. Select ENGINE 1 DATA LIST on scan tool and observe ECT sensor display. If scan tool display reads that engine coolant temperature reached 140°F (60°C), recheck system on a cold start and refer to DIAGNOSTIC AIDS . If scan tool display does not indicate that engine coolant temperature has reached 140°F (60°C), go to next step.
  6. Measure ECT sensor resistance. See appropriate SYSTEM & COMPONENT TESTING article. If resistance is as specified, go to next step. If resistance is not as specified, go to step  8.
  7. Check thermostat operation, coolant level, coolant mixture ratio and cooling fan operation. Repair as necessary. After repairs, go to step  9.
  8. Replace ECT sensor. See ENGINE COOLANT TEMPERATURE SENSOR  After repairs, go to next step.
  9. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0126. 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.
  10. 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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