Transmission Fluid Temperature Sensor 1 - Voltage Above Normal/Shorted to High Source
The transmission fluid temperature sensor is reading too high, indicating a potential issue with the sensor or wiring.
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What it means (plain English)
The computer monitors the transmission fluid temperature through a sensor. If it sees a voltage over about 4.5 volts when it should be lower, it triggers this code, thinking the fluid is too hot or the sensor is malfunctioning.
What the computer is actually seeing
When the transmission fluid temperature exceeds 4.5 volts, the ECM notes this and sets SPN 0731.
What a healthy reading looks like
Normal range for transmission fluid temperature is typically 80-150°C (176-302°F). The sensor output voltage should be between 0.5 to 4.5 volts depending on fluid 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 the transmission fluid level; ensure it's within the specified range. If low, top it off and test drive to see if the code returns.
- 22. Inspect the wiring and connectors leading to the transmission fluid temperature sensor for any signs of damage or corrosion. Repair any issues found.
- 33. Measure the voltage at the sensor connector with the ignition on. If it's above 4.5 volts with the engine off, suspects a short in the wiring.
- 44. With the transmission at normal operating temperature, check the sensor output voltage directly. It should be in the expected range (0.5-4.5 volts). If it's out of range, replace the sensor.
- 55. If the issue persists, test the TCM for proper operation; refer to manufacturer specifications.
Common causes
- Failed transmission fluid temperature sensor
- Wiring harness short to power
- Corroded connectors
- Low transmission fluid levels
- Faulty transmission control module (TCM)
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not advisable to drive with this code if the transmission is overheating, as it can lead to damage.
Will this code come back after I clear it?
If underlying issues are not resolved, the code is likely to return.
Why does this code often pair with transmission slipping?
Overheating can cause the transmission fluid to lose its viscosity, resulting in slippage.
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