PCM / ECM / TCM Internal Temperature Sensor Circuit High
The engine computer's internal temperature sensor is reading too high, like a thermometer stuck in the sun. This prevents the PCM from accurately managing engine functions that depend on its own operating temperature.
The PCM monitors its own internal die temperature using an on-chip thermistor to adjust processing speed and fuel delivery calibration. When the voltage signal exceeds the upper threshold, it indicates either excessive heat buildup or a sensor circuit malfunction. The ECU uses this reading to protect itself from thermal damage.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| PCM Temperature Sensor Voltage | 0.5–2.5V (roughly 40–120°C) | >2.5V (excessive temperature signal) |
| PCM Die Temperature | <130°C operating safe zone | >150°C (triggers fault code) |
Code P0669 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0669 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.