Transmission Fluid Temperature Sensor 1
Indicates an issue with the transmission fluid temperature sensor signal.
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What it means (plain English)
The transmission fluid temperature sensor measures how hot the fluid is. If the reading is off, it could mean the sensor is bad or the fluid is too hot.
What the computer is actually seeing
The engine control unit (ECU) expects a voltage signal from the temperature sensor that typically ranges from 0.5V (low temp) to 4.5V (high temp). If the voltage is outside of this range or drops unexpectedly, a fault code is set.
What a healthy reading looks like
Expect the transmission fluid temperature to be between 150°F to 220°F when operating normally. Voltage from the sensor should be in the range of 0.5V to 4.5V based on the temperature.
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 fluid or replace if low or dirty. Decision: Is the fluid level normal? (Yes/No)
- 22. Inspect wiring and connectors leading to the transmission temperature sensor for damage or corrosion. Decision: Are all connections secure and in good condition? (Yes/No)
- 33. Use a multimeter to check voltage at the sensor connector with the ignition ON (engine OFF). You should see a signal voltage between 0.5V and 4.5V. Decision: Is the voltage within the expected range? (Yes/No)
- 44. If the voltage is out of range, replace the sensor. Decision: Did replacing the sensor clear the code? (Yes/No)
Common causes
- Faulty transmission fluid temperature sensor
- Wiring issues (shorts, opens)
- Connector corrosion or damage
- Low transmission fluid level
- Contaminated transmission fluid
Typical repair cost
$$-$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderate severity; it's better to address it soon to avoid transmission issues.
Will this code come back after clearing?
If the underlying issue remains unresolved, yes, it'll likely return.
Why does this code pair with others?
Transmission faults often have multiple related codes due to interdependencies in sensor readings.
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