FMI 13 - Fluid Temperature Sensor
The fluid temperature sensor is reporting an issue.
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What it means (plain English)
The temperature sensor for the fluid is giving incorrect readings, making the computer think the fluid is either too hot or too cold when it shouldn't be.
What the computer is actually seeing
The engine control module (ECM) interprets the voltage signal from the fluid temperature sensor, which varies based on the temperature of the fluid. If the signal stays high (above 4.5V) or low (below 0.5V) for too long, the ECM triggers a fault code.
What a healthy reading looks like
The normal voltage range from the sensor is between 0.5V to 4.5V, corresponding to a fluid temperature range of approximately -40°C to 150°C (-40°F to 302°F).
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check fluid level and type to ensure it's correct for the application.
- 22. Inspect the wiring and connectors between the fluid temperature sensor and ECM for damage, corrosion, or disconnections.
- 33. Measure the voltage at the sensor connector: expect 0.5V to 4.5V while the engine is running. If outside this range, replace the sensor.
- 44. Use a scan tool to check for additional fault codes that might point to other related issues.
- 55. If voltage readings at the sensor are normal but fault persists, check the ECM for faults.
Common causes
- Faulty fluid temperature sensor
- Wiring issues (broken, shorted, corroded)
- Connector problems (loose, dirty contacts)
- Faulty ECM
- Incorrect fluid use or level issue
Typical repair cost
$$
Related codes
Frequently asked questions
Can I drive the vehicle with this code present?
It's generally drivable but monitor for overheating or performance issues; fix soon.
Will this code clear itself?
It may clear if the issue resolves, but often requires manual resetting after repair.
Why does this code appear with other codes?
It can signal a broader temperature or sensor issue in the system, affecting multiple parameters.
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