Car won't go over 80mph.. Needing some help!!

[Mike Pfeifer]

I do feel like these codes are a good place to start with. They appear to be related to the PCM and its communication with stability control. These two systems have to talk to each other in order to function correctly. As an example, the stability control needs to command the PCM to cut power in certain circumstances. If that communication is not working properly, it may limit to a “more safe” range of operation. I’m not familiar with how exactly this communication works on the S550, but should be a digital bus. Likely a CAN bus of some sort. So you will need to diagnose that. It may be a synchronization thing, a programming error, a faulty module, or even a physical wire fault. I think my first steps would be a battery reset first, followed by reflashing the PCM and/or stability control. After that, it’s gonna be time to start measuring what’s going on on that bus.

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[Skye]

https://www.mustang6g.com/forums/threads/80mph-speed-limiter.123343/

needed BCM reset at dealer or someone with forescan

There was a corruption uploading the tune and the BCM module controls the speed limiter apparently

hope this helps

@Allan_OC had the same issue as the OP. In the thread above , he did fix the problem.

Allan's thread also makes reference to the U2100 and U0122 codes being discussed.

 

[Mach VII]

https://www.mustang6g.com/forums/threads/80mph-speed-limiter.123343/



@Allan_OC had the same issue as the OP. In the thread above , he did fix the problem.

Allan's thread also makes reference to the U2100 and U0122 codes being discussed.

Yep, that matches up with thread I referenced but with far more detail.... good find!

 

[MostHated5.0]

https://www.mustang6g.com/forums/threads/80mph-speed-limiter.123343/



@Allan_OC had the same issue as the OP. In the thread above , he did fix the problem.

Allan's thread also makes reference to the U2100 and U0122 codes being discussed.

Okay after reading the thread, we may be onto something. I have received a "Controller Unlocker: TImed Out" message before whenever I would download a tune to my car. I would just "write" it again and it would download fine the second time. Just wondering if this has had something to do with the behavior of the car now? Plus I have had those two codes in the system regularly but they never turned on the CEL.

He had to do a BCM reset if I'm not mistaken or read it wrong...
I'm wondering if that will fix my problem, and how could I do it without a forscan tool? Just hope the car doesn't need another PCM or even a BCM at this point. But if that's the problem then so be it. Just need this problem fixed!

Thanks for all of the advice and help guys! I will report back what I find once it's done..

 

[agmattocks]

Check your rear hubs. Jack up the car at the rear and see it your wheels tilt in and out by hand.

 

[Allan_OC]

Car won't accelerate any higher than 80mph. IT'S QUITE ANNOYING!! I have two key fobs and it shows that I have two admin keys in my settings. Really about ready to throw in the towel with this car.

Gen 3 mustang gt with the 10 speed trans...

Any advice or help would be much appreciated! What am I missing here? I keep hearing key fobs, key fobs, key fobs. Is there something else that could be causing this limp mode or speed limiter to cut me off at 80mph?

Thanks!

OP

whoever uploaded a tune corrupted the BCM whether or not it was noticed but this is the exact same problem

pay a dealer the $125 diagnostic fee (I know pita) but you will thank yourself.

sometimes for unknown reasons the BCM locks the MPH to under 80

uploading/reverting back to stock will do nothing for you. I spent a solid week trying to trouble shoot this and in the end, I reverted back to stock and had the BCM cleared. Not sure what the code was exactly but this was the fix.

not the end of the world and be careful when you are uploading your tune that you do not disconnect the device and you are within WiFi range depending on what delivery method you are using (HP/Sct/lund/etc)

Hope this helps

 

[sk47]

Hello; Many years (decades) ago I had a speed limited car. 1957 Chevy. Turned out to be a weak manual fuel pump. Ran fine up to a particular speed. This is an old school thing to be sure so likely will not apply.
Question= have you tried to run in different gears? Does it stall at 80 in all upper gears?

Was with a friend one evening. The car went into limp mode and would not go faster than 5 mph. Limped to a friend's house. Then removed a battery cable for ten minutes or so. After that the car ran normally and has for maybe 20 years. I suspect clearing codes might do the same thing but wonder???

 

[K Myers]

Car won't accelerate any higher than 80mph. IT'S QUITE ANNOYING!! I have two key fobs and it shows that I have two admin keys in my settings. Really about ready to throw in the towel with this car.

Gen 3 mustang gt with the 10 speed trans...

Any advice or help would be much appreciated! What am I missing here? I keep hearing key fobs, key fobs, key fobs. Is there something else that could be causing this limp mode or speed limiter to cut me off at 80mph?

Thanks!

Get your battery teated

 

[MostHated5.0]

Week later.. I tried some more things and still no better.

Ordered Forscan and disabled my key feature.
Did a bcm reboot/reset with Forscan and cleared codes.
Removed dyno plug and test drove car to see if possible abs sensor issue, but no change.

Tuner claims that it's not pcm related from what he is seeing in my logs I've sent him. Idk
When accelerating, once I get to 80, my gas pedal can be like wot or even close to that, and it's like the computer isn't sensing any more movement to opening. Up and down hills while driving, it will decelerate but will not go over 80 even going downhill.

 

[BlkMach10510]

Week later.. I tried some more things and still no better.

Ordered Forscan and disabled my key feature.
Did a bcm reboot/reset with Forscan and cleared codes.
Removed dyno plug and test drove car to see if possible abs sensor issue, but no change.

Tuner claims that it's not pcm related from what he is seeing in my logs I've sent him. Idk
When accelerating, once I get to 80, my gas pedal can be like wot or even close to that, and it's like the computer isn't sensing any more movement to opening. Up and down hills while driving, it will decelerate but will not go over 80 even going downhill.

Can you remove the tune and then take it to ford to see if they can find anything?

 

[Cobra Jet]

So, the only other 3 things I can think of:

1) Gas pedal - isn’t the gas pedal a “switch” now in these new vehicles? It’s no longer drive by cable but drive by “wire”, where the motion of the gas pedal input is fed back to the PCM…. If the gas pedal is malfunctioning, it’s not feeding the correct signal back to the PCM.

2) Malfunctioning throttle body

3) The brake pedal (or clutch pedal) “bumpers” if missing or have become deteriorated, will also cause multiple operational issues. The threads for that topic is here:
https://www.mustang6g.com/forums/th...edal-bumper-nhtsa-recall.172153/#post-3670904

and

https://www.mustang6g.com/forums/threads/brake-light-switch-near-pedal-failure.122100/

 

[Allan_OC]

FYI I’ll wait for the OP to post however BCM flash with Ford fixed his issue…….

 

[MostHated5.0]

Update on the problem I was having...

Did a PMI on the pcm and software update today. The codes are cleared and speed limiter is now gone. Damn corrupted files!

Thanks to everyone who offered advice

 

[Cobra Jet]

Update on the problem I was having...

Did a PMI on the pcm and software update today. The codes are cleared and speed limiter is now gone. Damn corrupted files!

Thanks to everyone who offered advice

So you were on a stock PCM and somehow it got corrupted?? Can you elaborate a little more? Did it get corrupt during a service center update or some type of Forscan attempt?

 

[mindo389]

One of the first rules of programming: garbage in, garbage out. Glad you got it figured out. But like Cobra Jet asked, how did you get a corrupted program?

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