U0667 indicates that the powertrain control module (PCM) has lost communication with the engine oil temperature sensor (EOTS). The sensor provides the PCM with oil temperature data used for engine management, and when the signal is missing the PCM sets this code.
The sensor itself may be internally open or shorted, preventing it from sending a valid signal to the PCM.
Corrosion, bent pins, or loose fit at the sensor harness connector can interrupt the communication line.
An open circuit, short to ground, or short to voltage in the harness between the sensor and PCM can cause loss of communication.
If the sensor does not receive proper voltage or ground, it cannot operate and the PCM sees no signal.
A malfunction inside the PCM’s communication circuit for this sensor is possible but uncommon; it should be considered only after wiring and sensor checks.
Corrupted PCM firmware could falsely report a lost communication, though this is seldom the root cause.
No. The PCM is rarely at fault for this code; most cases are due to the sensor, its connector, or wiring. Replacing the PCM should only be considered after those components have been tested and found good.
Clearing the code without fixing the underlying communication loss may hide a problem that could affect engine management, especially under extreme temperatures. It is advisable to diagnose and repair the cause rather than just clearing the code.
The sensor is usually threaded into the engine block or oil pan near the oil filter, but exact location varies by vehicle; consult the service manual for the specific model.
Not directly. The PCM uses oil temperature for functions like variable valve timing and idle speed control; loss of the signal may lead to suboptimal operation but does not by itself cause overheating.