What it means
Same as P0666 with the signal voltage above the plausible range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
The PCM, ECM, or TCM uses an internal temperature sensor circuit to monitor heat within the module. P0669 sets when the sensor A circuit signal is above the expected electrical range, commonly because the circuit is open or its signal is shorted to a supply.
Common causes
Most likely first.
- Sensor internal open
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
How to diagnose it
- Save freeze-frame data and scan all modules for related power or communication faults before clearing codes.
- Check the reported module temperature for a fixed, implausibly high, or missing reading.
- Inspect the module connector and accessible wiring for an open connection, corroded or pushed-back pins, damaged insulation, or contact with a power source.
- Following vehicle service information, check circuit continuity and test for a short to supply with the module and circuit safely isolated.
- Verify module power and ground against the manufacturer's specification; if external tests pass, investigate an internal sensor or module fault.
Common fixes
- Repair an open or damaged sensor-circuit wire.
- Repair connector terminals with corrosion, poor contact, or pin displacement.
- Separate and repair wiring shorted to a supply source.
- Repair or replace the control module if its internal sensor circuit is confirmed faulty.
- Perform any required module reset or relearn after repair.
Can I keep driving?
If the vehicle runs normally, keep driving brief and gentle until the fault is diagnosed, since the module may not be monitoring its temperature correctly. Avoid a long or demanding trip, and stop if the vehicle stalls, enters limp mode, or will not restart.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.