What P0197 means
The engine oil temperature sensor A is an NTC thermistor fed with 5 V through a resistor: the hotter the oil, the lower the signal voltage.
How the engine computer detects it
The engine module uses the oil temperature for variable cam timing (Ford disables it with cold oil or a sensor fault), engine protection and the oil life monitor; many engines have no such sensor and use a calculated oil temperature instead. P0197 means the signal voltage is below its lower limit, so the module would read implausibly hot oil (around 145–150 °C (293–302 °F)) – practically always a signal wire shorted to ground or an internally shorted sensor. Ford sets it below 0.16–0.20 V for 5 s; GM below 25 Ω in 20 of 50 samples – without a warning light on the 2018 LT4, with two trips on the 2019 version, so MIL behavior depends on the manufacturer and model year. A substitute value is used.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on (depending on manufacturer)
- Oil temperature display at maximum or oil temperature warning
- Fan running constantly or power reduction possible
- Restricted cam timing (Ford)
Common causes
- Signal wire chafed against ground or the engine block Most likely
- Sensor shorted internally Possible
- Oil or water in the connector (leakage current) Possible
- Control module input faulty Less likely
How to diagnose P0197
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: engine oil temperature sensor, sensor wiring.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 1
- Fuel and air metering
- 97
- Specific fault
Questions drivers ask
Can I drive with code P0197?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P0197?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0197 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P0197 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: easy. Start with the cheapest checks before replacing expensive parts.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.