Engine Oil Temperature Sensor High
P0198 indicates the engine oil temperature sensor is reading a voltage signal that is higher than the PCM's expected range, suggesting the sensor may be failing or there is an electrical wiring issue. This code can appear alongside coolant temperature codes and may indicate an engine overheat condition, so prompt diagnosis is important.
What You Might Notice
- Illuminated Check Engine Light
- Engine running hot or overheating
- Difficulty starting or rough idle
- Reduced fuel economy or poor performance
- Fan running continuously or not running properly
Most Common Causes
- 1
Faulty Engine Oil Temperature Sensor
The sensor may be internally damaged or have a failed internal resistor, causing it to send an abnormally high voltage signal to the PCM. This is the most common cause of P0198.
- 2
Wiring Problems
Corroded, damaged, or shorted wiring in the sensor circuit can cause high voltage readings. Check the harness and connectors for corrosion or breaks.
- 3
Engine Cooling System Problems
Actual engine overheating from coolant leaks, thermostat failure, or water pump issues can cause the sensor to read legitimately high temperatures. Address cooling system issues first.
- 4
Faulty PCM or Circuit Board Issue
In rare cases, the PCM itself may have a defective input circuit or the sensor circuit board may be damaged, misinterpreting normal sensor signals as high voltage.
How to Diagnose It
- 1
Check Faulty Engine Oil Temperature Sensor — The sensor may be internally damaged or have a failed internal resistor, causing it to send an abnormally high voltage signal to the PCM. This is the most common cause of P0198.
- 2
Check Wiring Problems — Corroded, damaged, or shorted wiring in the sensor circuit can cause high voltage readings. Check the harness and connectors for corrosion or breaks.
- 3
Check Engine Cooling System Problems — Actual engine overheating from coolant leaks, thermostat failure, or water pump issues can cause the sensor to read legitimately high temperatures. Address cooling system issues first.
- 4
Check Faulty PCM or Circuit Board Issue — In rare cases, the PCM itself may have a defective input circuit or the sensor circuit board may be damaged, misinterpreting normal sensor signals as high voltage.
How to Fix It
- 1
Inspect and Test Engine Oil Temperature Sensor
Locate the engine oil temperature sensor, disconnect it, and use a multimeter to test its resistance at different temperatures. Compare readings to manufacturer specifications. If readings are out of range, replace the sensor.
- 2
Check Wiring and Connectors
Inspect the sensor harness and connectors for corrosion, damage, or loose connections. Clean corroded connectors with electrical contact cleaner and ensure all connections are tight. Replace any damaged wiring.
- 3
Inspect Engine Cooling System
Check coolant level, hoses for leaks, radiator condition, and thermostat operation. Verify the cooling fan is functioning properly. Address any cooling system issues that may cause actual overheating.
- 4
Check PCM and Circuit Board
If the sensor and wiring test good but the code persists, have the PCM scanned for internal faults or consider professional diagnostics to check the sensor input circuit on the engine control module.
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