What Does P0198 Mean?
This code indicates the engine oil temperature sensor is reading higher than the ECM expects, either because the signal voltage corresponds to an abnormally high temperature or the circuit has a low-resistance fault. For NTC sensors, a high temperature reading corresponds to low resistance. The ECM sets this code when the reported oil temperature exceeds a maximum threshold, such as 300 degrees F or higher.
Common Causes
35%
Shorted engine oil temperature sensor with abnormally low resistance causing the ECM to interpret an excessively high temperature
25%
Signal wire shorted to ground in the wiring harness, pulling the sensor voltage low and simulating a high temperature reading
25%
Genuinely elevated engine oil temperature from low oil level, degraded oil, faulty oil cooler, or persistent engine overheating
15%
Water intrusion in the sensor connector causing a low-resistance path between signal and ground terminals
Diagnostic Steps
1
Step 1: Check the oil temperature PID on a scan tool. If it reads above 300 degrees F when the engine is cold or at normal operating temperature (verified by coolant temp), the sensor or circuit is faulty.
2
Step 2: Verify engine oil level is correct and oil condition is acceptable. Low oil level can genuinely cause elevated oil temperatures. Top off and recheck if needed.
3
Step 3: Disconnect the oil temperature sensor connector and check if the PID drops to a very low temperature (indicating open circuit). If so, the sensor is internally shorted; replace it.
4
Step 4: With sensor disconnected, measure resistance across sensor terminals. Compare to specification (typically 70-100 ohms at 250 degrees F for NTC type). A near-zero reading confirms internal short.
5
Step 5: If sensor resistance is normal, check the signal wire for shorts to ground by measuring resistance from the signal pin at the ECM connector to chassis ground. Should read OL (open). Low resistance indicates a wiring short.
Estimated Repair Cost
$60 - $250
Parts + labor, varies by vehicle and location
This code indicates the engine oil temperature sensor is reading higher than the ECM expects, either because the signal voltage corresponds to an abnormally high temperature or the circuit has a low-resistance fault. For NTC sensors, a high temperature reading corresponds to low resistance. The ECM ...
The most common cause of P0198 (Engine Oil Temperature Sensor High) is: Shorted engine oil temperature sensor with abnormally low resistance causing the ECM to interpret an excessively high temperature
Typical repair costs for P0198 range from $60 to $250, depending on the vehicle, location, and whether you do it yourself or go to a shop.
If the oil temperature is genuinely elevated, continued operation can cause rapid engine oil breakdown, bearing damage, and catastrophic engine failure. The root cause must be confirmed before dismissing as a sensor fault.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0198 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Lubrication/Management System
Difficulty
Type
Generic (SAE)
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