Faulty engine oil temperature sensor giving an incorrect low-voltage signal.; Damaged or corroded wiring harness or connector at the sensor, including chafed wires or pushed-out terminals.; Open circuit in the signal wire between the sensor and the ECM, often due to a broken wire or poor splice.; Short to ground on the signal circuit, which pulls the voltage below the expected range.; Contaminated or degraded sensor tip from old oil or sludge, causing inaccurate readings.; ECM internal fault or corrupted software, though this is less common than sensor or wiring issues.; Poor electrical ground for the sensor return circuit, leading to a voltage offset.

DTC codes / P01xx · Fuel and air metering / P0197

P0197Engine Oil Temperature Sensor Low

Q: What does code P0197 mean?

Engine Oil Temperature Sensor Low. P0197 means the engine control module (ECM) has detected a voltage signal from the engine oil temperature (EOT) sensor that is lower than the expected range for the current operating conditions. The ECM interprets this low voltage as an excessively high oil temperature or an open/shorted sensor circuit, and it sets the code to alert the driver while substituting a default oil temperature value for strategy calculations.

P0197 means the engine control module (ECM) has detected a voltage signal from the engine oil temperature (EOT) sensor that is lower than the expected range for the current operating conditions. The ECM interprets this low voltage as an excessively high oil temperature or an open/shorted sensor circuit, and it sets the code to alert the driver while substituting a default oil temperature value for strategy calculations.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illumination of the check engine light (MIL) on the dashboard.
Often no symptoms besides the warning light, especially if the sensor fails gradually.
Oil temperature gauge or display may read abnormally high or stay pegged at the low end, depending on the vehicle's gauge strategy.
Possible reduced engine performance or altered shift quality if the ECM uses oil temperature for protection strategies.
In rare cases, a message on the driver information center indicating an oil temperature sensor fault.
No noticeable change in oil pressure or engine noise, since the sensor only reports temperature and does not control oil flow.

Common causes, most likely first

Faulty engine oil temperature sensor giving an incorrect low-voltage signal.
Damaged or corroded wiring harness or connector at the sensor, including chafed wires or pushed-out terminals.
Open circuit in the signal wire between the sensor and the ECM, often due to a broken wire or poor splice.
Short to ground on the signal circuit, which pulls the voltage below the expected range.
Contaminated or degraded sensor tip from old oil or sludge, causing inaccurate readings.
ECM internal fault or corrupted software, though this is less common than sensor or wiring issues.
Poor electrical ground for the sensor return circuit, leading to a voltage offset.

How to diagnose and fix it

Use an OBD-II scan tool to read the engine oil temperature sensor voltage and compare it with a known-good value or a infrared thermometer reading at the oil pan.
Visually inspect the sensor connector and wiring for corrosion, loose pins, or physical damage, and repair as needed.
Measure resistance across the sensor terminals and compare with the manufacturer's temperature-resistance chart to confirm sensor accuracy.
Check for continuity and short-to-ground on the signal wire from the sensor to the ECM, repairing any open or shorted sections.
Verify the sensor return circuit has a good ground, cleaning or tightening grounds as necessary.
If the sensor and wiring test good, substitute a known-good sensor or use a resistor box to simulate the correct signal and see if the code clears.
Clear the code and perform a road test to confirm the repair, monitoring live oil temperature data for normal behavior.

Oil temperature sensor low voltage traps

A low-voltage code often results from an open circuit rather than a failed sensor, so technicians who replace the sensor without checking wiring frequently see the code return.
Oil temperature sensors share design and failure modes with coolant temperature sensors, but their location in the oil pan or block makes them vulnerable to sludge and debris that can skew readings.
The ECM may use oil temperature to enable or disable certain functions such as variable valve timing or cylinder deactivation, so a faulty signal can cause drivability issues that seem unrelated to oil temperature.
On some vehicles, the oil temperature sensor is integrated into the oil level sensor or oil pressure sensor, so a low oil temperature code may actually point to a fault in a combined unit.
A poor engine ground can cause a low-voltage signal on the sensor return circuit, mimicking a sensor failure and leading to misdiagnosis if grounds are not checked.

Can I keep driving with P0197?

You can generally continue driving with P0197 because the ECM substitutes a default oil temperature value and the engine remains protected by other sensors. Avoid heavy towing or sustained high-speed driving until the fault is repaired, as the ECM may not accurately monitor oil temperature for extreme conditions.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.