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P0667PCM/ECM/TCM Internal Temperature Sensor Circuit Range/Performance

The control module's internal temperature sensor is producing a reading that doesn't make sense compared to other temperature data or expected warm-up behavior.

Definition

The engine or transmission control module cross-checks its internal temperature sensor against plausibility limits — for example, comparing it to intake air and coolant temperature after a long cold soak, when all should read near ambient. P0667 sets when the internal sensor is electrically alive but its value is stuck, drifts unrealistically, or disagrees with those references beyond an allowed margin. The MIL illuminates and, depending on how the module uses the value, fan operation, driver-stage protection, or temperature-compensated outputs may be affected; most vehicles show no obvious driveability symptom. Because the sensor is internal, a persistent fault generally condemns the module itself once power and ground supplies are verified.

Common causes

  • Drifted or degraded internal temperature sensing element in the module
  • Module overheating due to poor mounting location, blocked cooling airflow, or nearby exhaust heat
  • High-resistance module power or ground connections offsetting the sensed value
  • Internal moisture intrusion or circuit-board corrosion
  • Outdated module calibration with overly tight rationality limits

Common misdiagnoses

  • Replacing the ECT sensor because 'temperature sensor' is in the code description
  • Replacing the IAT or ambient air temperature sensor
  • Replacing the thermostat or cooling fans
  • Replacing the transmission fluid temperature sensor

Troubleshooting steps

  1. 1.Perform a cold-soak comparison

    After the vehicle sits overnight, compare the module internal temperature PID with IAT, ECT, and ambient PIDs; all should agree within about 5-8 degrees C.

  2. 2.Verify module power and ground integrity

    Voltage-drop test each feed and ground under load (under 0.1 V), since resistance in these circuits shifts the sensor's analog reference.

  3. 3.Monitor the PID during a drive

    Watch for the internal temperature freezing at one value or spiking implausibly fast — either behavior confirms the sensor rather than the environment.

  4. 4.Inspect the module's location and condition

    Confirm heat shields are present, cooling passages or fins are unobstructed, and there is no water entry at the connectors.

  5. 5.Check for TSBs and reflash if applicable

    Apply any updated calibration addressing internal temperature rationality faults before replacing hardware.

  6. 6.Replace the module if the fault returns

    With supplies verified and software current, a repeat P0667 means internal sensor drift, and the module must be replaced and programmed.

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