This is with my 96 so I dunno about the earlier models.
Hold the reset button on you gauge cluster.
Then turn the key to run and the speedometer like resets or something.
I don't know what the point of this is but I just thought it was neat.

 

Yeah, you can actually do some cool diagnostic stuff and play around with the computer settings through there. Theres directions on one of the mustang websites.

-Jon

 

anyone know what the point of that would be???

 

It's for resetting the speedometer calibration for your wheel size. i can type up the proceedure if you guys are interested, but be forewarned, the module can only be reset 6 times before it must be replaced.

Take care,
-Chris

 

WHAT?!? 6 TIMES?!?!I thought the little trick was kind of cool so I did it like 20 times?!?!Everything is ok still...sofar
Why would it need to be replaced?

 

You didn't perform the entire proceedure, so you should be alright, but I'd stop playing with it if I were you.

Take care,
-Chris

 

Chris,

I'd be interested in the procedure, my speedo. is off by about 5 mph. My truck had 35's already when I bought it, so I don't know the original tire diameter, or the converting factor. Can you help me out by tellin me the stock tire size for a '92 4x4 half ton? Thanks in advance!! I appreciate it.

 

PKRWUD could you please type u pthe procedure for recalibrating the speedo. Does this also work for changing the gears in the rear diff?

 

It only recalibrates for different tire sizes, not gear ratios. For gear ratios, you need to change the speedometer cable gear. Tell me what you have, and I'll tell you what you should have.

I'll start a new thread with the info.

Take care,
-Chris