What it means
The control module monitors the engine oil temperature sensor signal. It sets this code when the signal is lower than the circuit’s expected range.
At a glance
- Usually lights the check-engine light
How it works
The engine oil temperature sensor sends a voltage signal to the control module that corresponds to oil temperature. P0197 sets when the signal falls below the circuit's expected range, commonly because the signal is shorted to ground or the sensor has failed low.
Common causes
Most likely first.
- Signal wire shorted to ground
- Sensor failed
Symptoms
- Check-engine light on
- Oil temperature reading may be inaccurate or unavailable
How to diagnose it
- Review freeze-frame data and scan-tool oil-temperature data to see whether the low signal was present from startup or appeared during operation.
- With the ignition off, inspect the oil-temperature sensor connector for corrosion, damaged pins, oil intrusion, or a loose fit.
- Trace the signal wire for chafing or contact with ground, focusing on harness bends and areas near hot or moving parts.
- Using the wiring diagram, check the sensor supply and ground and test the signal circuit for a short to ground or an open.
- If wiring and connector checks pass, test the oil-temperature sensor output against the manufacturer's specification to confirm whether it has failed low.
Common fixes
- Clean and secure the oil-temperature sensor connector terminals.
- Repair the signal wire where it is shorted to ground or damaged.
- Restore a faulty sensor supply or ground connection.
- Replace the engine oil temperature sensor if its signal remains low with an intact circuit.
Can I keep driving?
The displayed oil temperature may be inaccurate or unavailable, so pay attention to any oil or overheating warnings. Avoid heavy loads if the engine seems unusually hot and arrange diagnosis before relying on the reading.
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.