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 usually means the sensor is reading an abnormally high temperature or there is a short to voltage in the sensor circuit. The EOT sensor is a thermistor that changes resistance with temperature; high voltage corresponds to low resistance, which can be caused by a faulty sensor, wiring issues, or a short circuit.
1. Most Common Causes
- Faulty engine oil temperature sensor
- Short to voltage in the sensor circuit
- Open or shorted wiring or connector issues
- Corroded or damaged sensor connector
- ECM failure (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine may run poorly or have reduced power
- Possible overheating or inaccurate temperature gauge
- Increased fuel consumption
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for additional codes.
Step 2: Visually inspect the EOT sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's resistance with a multimeter; compare to manufacturer specifications at known temperatures.
Step 4: Check for voltage at the sensor connector; should be around 5V reference. If higher, suspect a short to voltage.
Step 5: If sensor and wiring are okay, test the ECM's ability to read the sensor by backprobing the signal wire.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can lead to engine overheating or damage. The ECM may use a default temperature value, which can affect engine performance and fuel economy.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, including parts and labor. The sensor itself is usually inexpensive ($20-$50), and labor is about 0.5-1 hour.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.