P0198: Engine Oil Temperature Sensor High

What it means

Engine oil temperature sensor signal exceeds maximum. Shorted to voltage, open ground or open sensor.

At a glance

• Usually lights the check-engine light

How it works

The engine oil temperature sensor provides the control module with a signal representing oil temperature. P0198 sets when that signal is above the circuit's expected range, which may result from a signal wire shorted to voltage, a broken ground path, or an open sensor.

Common causes

Most likely first.

1. Signal wire shorted to voltage
2. Sensor open-circuit

Symptoms

• Check-engine light on
• Oil temperature reading may be inaccurate or unavailable

How to diagnose it

1. Check freeze-frame data and live oil-temperature readings to determine whether the high signal appeared immediately or during warm-up.
2. With the ignition off, inspect the oil-temperature sensor connector for corrosion, loose pins, or damage that could interrupt its ground path.
3. Inspect the signal wire for contact with a power feed and the ground-reference wire for breaks or poor connections.
4. Use the wiring diagram to test the sensor circuit for a short to voltage and verify ground continuity to the manufacturer's specification.
5. If the circuit is intact, test the oil-temperature sensor for an open circuit using the manufacturer's procedure.

Common fixes

• Clean and secure corroded or loose sensor connector terminals.
• Repair the signal wire where it is shorted to voltage.
• Restore an open or poor ground-reference connection.
• Replace the engine oil temperature sensor if it is open and the wiring checks out.

Can I keep driving?

Treat an implausible oil-temperature reading as a loss of monitoring and heed any oil or overheating warnings. Avoid heavy loads if the engine shows signs of overheating, and arrange diagnosis before relying on the display.