Powertrain Control Module (PCM) Intermittent Conditions

Powertrain Control Module (PCM) Intermittent Conditions - The conditions that set the DTC are not present at this time. Duplicating the conditions under which the strored DTC set is very important when diagnosing an intermittent condition. Review the scan tool Freeze Frame Data information and when monitored conditions for the DTC being diagnosed.


If possible, pay particular attention to the ambient air temperature when the DTC set. Electrical connections, such as wire terminal connections, solder joints, and printed circuit board traces will expand and contract due to temperature changes. If the DTC was set in extreme cold conditions, the vehicle may need to be tested in extreme cold conditions.

Note : Power wire harness terminal connections are a big contributor to intermittent electrical connections. Follow the directions below to help identify the source of the intermittent electrical condition.

1. Record all DTC on the repair order.

2. Run a Vehicle scan report.

3. Perform any Service Bulletin or PCM flash update that may apply to the DTC that are present.

4. Use the scan tool to perform a system test if one applies to a failing component.

Warning : When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

5. With the ignition on or running, monitor the scan tool parameters related to the DTC  while wiggle testing the wiring harness. Lock for parameters values to change and/or a DTC to set.

Note : Using a data recorder and/or a lab scope may help diagnose intermittent conditions

6. If numerous trouble codes were set, use a wire schematic and look for any common sensor supply or ground circuits.

7. Perform a voltage drop test on the related circuits between the suspected inoperative component and the PCM.

8. For communication DTC, perform the scan tool ''Loss of comm test''. This will force the modules on the CAN C bus to continuously ping each other every one second. Wiggle the applicable wires while reading the NUMBER OF NO RESPONSE. A value above 0 indicates the location of a circuit fault.

9. Turn the ignition off.

10. Visually inspect the related wire harness. Disconnect all of the related component and in-line harness connector and check for the following :
  • Proper wiring harness routing.
  • Chafed, pierced, pinced, partially broken or open wiring harness insulation.
  • Wiring or wiring stands broken inside of the insulation.
  • Visually inspect the connector casings, lock, and weatherproof seal for any damage or water intrusion.
  • Visually inspect for broken, bent, pushed out, or correded terminals.
  • Visually inspect the connectors and terminals for overheating due to a poor connection (terminal may be discolored due to excessive current draw).
  • Verify correct connector pin fit at the related connector (drag test).
  • Connect all the related module, component and in-line wiring harness connectors and verify they are fully seated.

Caution : Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the PCM pinout box and PCM pinout box adafter to perform diagnosis.

11. Inspect and clean all PCM, engine, and chassis ground that are related to the DTC that are present.

12. For any relay DTC , actuate the relay with the scan tool and wiggle the related wire harness to try to interrupt the actuation.

13. For intermittent Evaporative Emission trouble codes perform a visual and physical inspection of the related parts including hoses and the fuel filler cap.

14. For intermittent misfire DTC check for restrictions in the intake and exhaust systems, proper installation of sensors, vacuum leaks, and binding components that are run by the accessory drive belt.

15. Check for any aftermarket and accessories and verify they are installed and operate correctly. If needed, disconnect them to verify they are not the cause of the problem.

Were any problems found during the above inspections ?

Yes, perform the necessary repairs, perform the Powertrain verification test.
No, test complete for PCM Intermittent Conditions.

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