Purchased a 2017 GT & found it was tuned.

This is a common problem -- buying a used car with a "mystery tune" and without the tuner device. Unfortunately this puts you in a difficult situation . . .

I assume you did not get the tuner device with the car. If you did get the tuner device with the car, then the factory tune should be on the tuner and you can download it from there.

However, if the car is modified, with modifications that REQUIRE a tune to run right, then it will not run right without the tune. The most common example is an aftermarket "cold air intake" where the mass air flow metering section is larger than stock, which requires a tune to "recalibrate" the mass air flow calculations, or the car will run lean.

So, first you need to find out if the car has any modifications that require a tune.

If it does not have any mods that require a tune, you can have it reflashed back to stock by a Ford dealer. I had this done in ~2011 (because I was in this situation) and they charged me about $150, if I remember correctly.

Why do you feel that you must go back to stock tune?

Skylerang said:

... took it to a ford dealership and they told me that reflashing could lock my pcm and told me if it did it would be 900 to replace it. ...

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I suppose that is possible, hopefully they were just warning you "just in case" .... it worked with no problem on my 2010 but I don't know if there are new issues in the later models that might cause a problem .... how much did they quote you for the factory tune reflash, assuming it did NOT lock the PCM?

Skylerang said:

I recently bought a 2017 mustang gt and it had a mystery tune didn’t find out about it until I went to get new tunes, the tuning company told me I’d need to reflash it back to stock for them to make the new tunes so I took it to a ford dealership and they told me that reflashing could lock my pcm and told me if it did it would be 900 to replace it. Any suggestions on what to do because I wasn’t sure if they were just feeding me bull do I have to spend that just too get new tunes?

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That's just fear mongering nonsense from the dealer. If you had the tuner device that should have been given to you then it would return the vehicle to the factory tune whenever you want. Actually, every time you would put a new tune on it the device would return the factory program to the PCM. It's a standard practice and assuming that the dealer does things by the book it won't do anything to the PCM.
If they try to tell you that the car's PCM locked up then I would demand to watch them reload it again and try to start the car as I would suspect that to be an instant bs story. I'm pretty sure that the dealers make you sign a waiver as standard practice but there's nothing to worry about imo. I don't think that I've ever heard of such a thing happening.

Cobrajet67 said:

That's just fear mongering nonsense from the dealer. ...

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... or maybe, looking at it in a more positive light, "an overabundance of caution" aka CYA ???

maybe talk to another dealer, if there is another one not too far away ... and it seems that smaller dealers can be more straightforward on this stuff, sometimes if you're lucky

JBert said:

I suppose that is possible, hopefully they were just warning you "just in case" .... it worked with no problem on my 2010 but I don't know if there are new issues in the later models that might cause a problem .... how much did they quote you for the factory tune reflash, assuming it did NOT lock the PCM?

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They quoted me $240 to factory reflash which I was okay with but then I left my mustang there and got a call later about it maybe locking my pcm which I was gonna just have them do it anyway but the pcm from them is $900 not including labor or them tuning the new pcm to my mustang so I’m assuming I’d be spending around $1200 just to go back to stock

$240 for less than an hour of time on their diagnostic machine is a total rip off. I wouldn't trust that dealer to change my oil. Shop labor is about $140 an hour anywhere you go. Is this dealer located in Beverly Hills or something?
I'm confused here. Did they or did they not tell you that the PCM is defective? What does maybe the PCM being locked up mean?
Just to flash the PCM back to stock isn't a big deal at all. My suggestion is to get your car out of that dealership ASAP.

Cobrajet67 said:

$240 for less than an hour of time on their diagnostic machine is a total rip off. I wouldn't trust that dealer to change my oil. Shop labor is about $140 an hour anywhere you go. Is this dealer located in Beverly Hills or something?
I'm confused here. Did they or did they not tell you that the PCM is defective? What does maybe the PCM being locked up mean?
Just to flash the PCM back to stock isn't a big deal at all. My suggestion is to get your car out of that dealership ASAP.

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That’s exactly what I thought 240 is a lot just to reflash to stock and my current pcm is fine nothing is wrong with it but they said if they reflash that something about doing that could lock the pcm I don’t know alot about the pcm or tuning but I know that’s a rip off, it’s a dealership in Tucson az when they told me that I got out of there to ask this forum what to do

I paid $150 to reflash mine back in 2011, if I remember correctly ... yeah $240 is a bit high

it's hard to tell if they were setting you up with the "reflashing might lock the PCM" thing or just giving you fair warning of what "might" happen

is there another dealer you can try? I'm thinking there must be more than one in the Tucson area