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Home >> Chevrolet >> 1997 >> C3500 HD 7.4 J, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (Engine Controls - Tests W/Codes - 6.5L) >> Diagnostic Trouble Codes >> DTC P0126 - Insufficient ECT For Stable Operation >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different variant/trim than selected.
  1. Perform Powertrain ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING - 6.5L DIESEL article. Then go to next step.
  2. Check if any engine coolant temperature DTC(s) are present. If other DTC(s) are present, diagnose using affected DTC test. If no other DTC(s) are present, go to next step.
  3. Turn ignition on, with engine off. Disconnect ECT 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 greater than -31°F (-35°C), diagnose using DTC P0117 test.
  4. Using a jumper wire, jumper ECT sensor harness connector terminals. If scan tool indicates ECT is greater than 302°F (150°C), go to next step. If ECT value is less than 302°F (150°C), diagnose using DTC P0118 test.
  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. Using DVOM, check ECT sensor resistance. See the SYSTEM/COMPONENT TESTS article. If resistance is not as specified, go to next step. If resistance is as specified, go to step 8).
  7. Check thermostat operation, coolant level, coolant mixture ratio and cooling fan operation. Repair as necessary. After checking cooling system, go to step 9).
  8. Replace ECT sensor. After replacing sensor, go to next step.
  9. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC that was set. 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, repeat step 2).
  10. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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