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2011 Mustang V6, Incorrect speed on speedo after software update

714 Views 2 Replies 2 Participants Last post by  Pete_Rockett
Hello, guys!

I've got 2011 Mustang V6 AT a months ago. Car with custom exhaust, cold air inlet and headers, and not standard wheels (255/45/R18).

Couple weeks ago i decided to update car sofware to fix kick between 1 and 2 gears. It was fixed successfully, but after that my speedo shows me incorrect speed, f.e. real speed 30 miles, but speedo shows 40, or if i run 150 km/h - spedo shows around 180 and i can not drive faster, because cars speed limit not allows me do that.

I guess, before software update there was right some values for speed sensor?

Please, what can i do to fix this? What parameters i have to reprogramm?

P.S. English is not my native language, so if you can not understand something - let me know, i will try to descibe.
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Ask your tuner to correct for the size tires you have etc. make sure that they have the proper gears in your tune for what you are really running, that will make a difference also.
Good luck.
Most likely the previous owner changed the rear axle ratio from the stock 2.73 to 3.73. If a dealer flashed the ECU then you lost that correction and you need an aftermarket tune.

What kind of cold air inlet was it? Was it long tube headers?
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