What Does P0669 Mean?
The PCM/ECM/TCM internal temperature sensor circuit is reading above the maximum expected voltage, indicating a high signal. This usually means the sensor is reporting an unrealistically cold temperature (or there is an open circuit in the internal sensor). The PCM cannot monitor its own thermal status, so it cannot protect itself from overheating. The driver may not notice immediate symptoms, but the module is vulnerable to undetected overheating.
Common Causes
45%
Internal temperature sensor failure within the control module (open circuit)
25%
PCM circuit board damage or cold solder joint at sensor connection
15%
Intermittent power supply issues affecting internal voltage reference
10%
Water or corrosion damage to PCM circuit board
5%
Software calibration error requiring reflash
Diagnostic Steps
1
Monitor the PCM internal temperature PID — if it reads -40°F or an unrealistically low value regardless of engine temperature, the internal sensor has an open circuit.
2
Check all PCM power supply and ground circuits for proper voltage and minimal drop (less than 0.1V on grounds). A voltage reference issue can cause all internal sensors to read incorrectly.
3
Inspect the PCM connector for bent or pushed-back pins, corrosion, or water damage. Check the housing seals for integrity.
4
Search for manufacturer TSBs regarding PCM internal temperature sensor issues — some have released software recalibrations or revised PCMs for this fault.
5
If all external circuits check good and no TSBs apply, the PCM will likely need replacement and reprogramming by a dealer or qualified facility.
Estimated Repair Cost
$200 - $1,600
Parts + labor, varies by vehicle and location
The PCM/ECM/TCM internal temperature sensor circuit is reading above the maximum expected voltage, indicating a high signal. This usually means the sensor is reporting an unrealistically cold temperature (or there is an open circuit in the internal sensor). The PCM cannot monitor its own thermal sta...
The most common cause of P0669 (PCM / ECM / TCM Internal Temperature Sensor Circuit High) is: Internal temperature sensor failure within the control module (open circuit)
Typical repair costs for P0669 range from $200 to $1,600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The PCM cannot monitor its own temperature, so it cannot protect itself from overheating. While drivability may be unaffected short-term, a genuinely overheating PCM that goes undetected could fail suddenly, causing engine stalling. Have this diagnosed within a week.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0669 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Control Module
Difficulty
Type
Generic (SAE)
Recommended Tools
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