FMI 6: Transmission Fluid Temperature High
Transmission fluid temperature is above normal operating range.
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What it means (plain English)
The temp sensor in the transmission is reporting higher than normal fluid temperatures, typically over 230°F (110°C), which can lead to transmission damage if not addressed.
What the computer is actually seeing
The transmission control module (TCM) monitors the temperature sensor signal. It expects a range between 170°F (77°C) to 230°F (110°C). Anything above 230°F triggers a fault code.
What a healthy reading looks like
Normal transmission fluid temperatures should be between 170°F (77°C) and 230°F (110°C).
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. Make sure it is within the specified range; if low, fill to proper level and check for leaks.
- 22. Inspect the transmission fluid for contamination or burnt smell; if fluid is dark or smells burnt, change the fluid and filter.
- 33. Test the temperature sensor using a multimeter; expected resistance should vary with temperature. At room temp, resistance should be around 13-15 ohms; replace if out of spec.
- 44. Inspect the coolant heat exchanger for blockages or leaks; clean or replace as necessary.
- 55. If all above check out, scan the TCM data to see real-time temperature readings; if temperatures are excessively high under normal conditions, consider internal transmission issues.
Common causes
- Low transmission fluid level
- Faulty coolant heat exchanger
- Debris restricting fluid flow
- Malfunctioning temperature sensor
- Internal transmission issues
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not recommended to drive long distances, as high transmission temperatures can cause damage.
Will this code come back after repairs?
If all related issues are resolved, the code should clear and not return.
Why does this code appear with other SPN codes?
Many transmission issues are related; high fluid temperature can indicate or cause other problems.
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