Transmission Temperature Sensor 1 Out of Range
Indicates the transmission temperature is outside of the acceptable range.
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What it means (plain English)
The computer is checking the transmission fluid temperature and sees a reading that’s too high or too low, which can lead to transmission damage if not addressed.
What the computer is actually seeing
The Engine Control Module (ECM) is reading the voltage signal from the transmission temperature sensor. A normal range is typically between 0.5V (cold) and 4.5V (hot).
What a healthy reading looks like
Transmission fluid temperature should normally be between 175°F and 230°F (80°C to 110°C) during operation.
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 transmission fluid level and condition; add or replace fluid if necessary.
- 22. Inspect wiring and connectors for the transmission temperature sensor; look for frays, corrosion, or loose connections.
- 33. Use a scan tool to check the actual temperature reading against the expected values; if reading is significantly out of range, replace the sensor.
- 44. If the readings are normal, consider checking the ECM for error codes or needing a software update.
Common causes
- Faulty transmission temperature sensor
- Wiring issues or poor connections
- Low transmission fluid level or quality
- ECM calibration faults
Typical repair cost
$$$
Related codes
Frequently asked questions
Can I drive safely with this code active?
It's best to fix this soon as it can lead to transmission overheating and potential damage.
Will this code come back after clearing?
If the underlying issue isn't fixed, it will likely return.
Why do I see this code with SPN 1903?
Both are related to transmission temperature sensors and could indicate a problem with the sensor circuit.
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