I have a 2011 Ford Fusion with the 6 speed trans.

How do I replace the transmission temp sensor? I'm throwing code p1783.

Engine: 3.0L. Transmission 6 speed semi automatic. Miles ~115k; Bought @ 53k. Had regular transmission flushes since then. Last one late 2015 @ maybe 70k. Have never replaced engine coolant but most mechanics have told me they don't even do that.

Symptoms: Wrench light comes on after 15 - 30mins of highway driving at speeds of 80mph or greater (totally okay on Chicago freeways).

When wrench light is on, fan up front is loud (notice it off hwy) and the throttle is touchy and seems to loose power. Touchy to the extent of it feeling like its slamming into a brick wall that isn't there (at times it's this bad).

I haven't checked the actual level but the fluid is red and doesn't smell burnt. I'd assume I'd be out of tranny fluid if it was leaking due to this being an ongoing issue since JAN 2016.

After 3 miles of off hwy driving, light comes off throttle acts fine, fan revs down. No codes are stored after the fact and the code has to be caught with the light on. I have a bluetooth odb I pulled it from.

Consulted with several people. The only two suggestions I get are vacuum leak and temp sensor.


  • What engine is in your Fusion? What makes you think the sensor is bad? How do you know the transmission is not overheating? How many miles are on it? When was the transmission last serviced?
    – CharlieRB
    Apr 7, 2017 at 15:28
  • @Quesofat what did you end up doing? I have the same 2011 Ford Fusion doing the exact same thing. Almost exact specs as what you said. I'm at about 112k miles now and dealer told me it would be about 2400 bucks to fix. Thanks
    – Mike King
    Jul 11, 2017 at 2:31
  • Rebuild is the only cure. It's lasted me 20k miles but I've stayed off the Hwy for the most part. I had a guy look at it in depth last week and said that he has no idea what is wrong, the torque converter is locking, the fluid is fine, the lines weren't clogged, the temp sensor was fine and there was no fluid coming out of the vents. He speculated that the pump was bad but said that is all internal. He told me he didn't feel comfortable fixing it until complete failure because it's lasted a year and a half or 20k miles. Maybe we should find a couple others and write letters to ford?
    – Quesofat
    Jul 11, 2017 at 2:41
  • Also the code is transmission over temp if you didn't already pull it. Also guy in Grayslake, IL quoted 1500, so there are cheaper rebuilds out there. I personally wouldn't bring it to the dealer. I wouldn't bring it to a chain transmission shop either though. A well reviewed independent guy will do a good job and be cheaper.
    – Quesofat
    Jul 11, 2017 at 2:43
  • Did you by chance ever have a PCM update?
    – Quesofat
    Jul 11, 2017 at 2:47

2 Answers 2


First and foremost, check the fluid level. Ensure it has enough, but NOT over full.

Check the transmission lines to the cooler (radiator) to make sure they are not damaged or pinched off. If there are no obvious physical issues that you can see, it is time to have it serviced. They can check internal fluid flow and pressures.

I don't think it is a sensor because it is sensing the over temp condition and running the fans. I also don't think it is a vacuum leak because that would be evident thru all modes of operation.

Since the highway stress causes issues and street driving allowed better performance, I am leaning toward it is not able to cool properly. That can be caused by low fluid or blockage to/from the cooler.

  • If it truly is overheating, do you think I have damaged the transmission after all of this? The fluid isn't burnt.
    – Quesofat
    Apr 7, 2017 at 17:41
  • No way to know that from an Internet post. I would suggest you limit driving it until you can get it resolved. Otherwise, you may damage it if it isn't already.
    – CharlieRB
    Apr 7, 2017 at 18:56
  • 1
    @Quesofat Even if it were a failure of the fluid temp sensor you probably wouldn't be able to service it yourself as it's built into the solenoid body. It also requires dealer level tools to flash the new solenoid body code into the PCM.
    – Ben
    Apr 7, 2017 at 20:49

If anyone comes across this for a 2011 Ford Fusion SEL. The issue was fixed by ensuring the transmission fluid levels were correct and more importantly a SOFTWARE UPDATE was done. Magically, the transmission ran a lot cooler.

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