Engine Oil Temperature Sensor High Input
The P0198 code indicates that the Engine Control Module (ECM) has detected a voltage signal from the engine oil temperature (EOT) sensor that is higher than the expected range, typically above 4.5 volts. This suggests the sensor is reading an abnormally high temperature or there is a circuit fault. The EOT sensor is a thermistor that changes resistance with temperature; high voltage usually means high resistance, which could be due to a faulty sensor, wiring issues, or a poor connection. This code can affect engine performance and may trigger limp mode.
01. Most Common Causes
- Faulty engine oil temperature sensor
- Open or shorted wiring in the sensor circuit
- Poor electrical connection at the sensor or ECM
- Corroded or damaged connector pins
- ECM failure (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine may run poorly or hesitate
- Reduced fuel economy
- Possible engine overheating indication
- Engine may enter limp mode
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for other related codes.
Step 2: Visually inspect the EOT sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor resistance with a multimeter; compare to manufacturer specifications at known temperatures.
Step 4: Check the voltage signal at the sensor connector with the ignition on; should be around 5V reference and a varying signal.
Step 5: If sensor and wiring are okay, test the ECM for proper operation or perform a continuity test between sensor and ECM.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as it can lead to engine damage due to incorrect oil temperature readings affecting lubrication and cooling. You may notice reduced performance or limp mode.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, including parts and labor. The sensor itself is usually $20-$50, and labor is about $30-$100 depending on vehicle accessibility.