i noticed on my 2008 MCs cabio that my speedo and on tach is reading 4mph faster then my TomTom gps also i use the Torque android app with elm327 bluetooth adapter hooked to esc and both show same speed but 4mph slower.

how do i fix this?

 

That's normal. There's a thread here, somewhere, talking about that. It has something to do with a law that prohibits a speedometer from reading lower than actual speed, but not higher.

You can get bigger tires to compensate.

Dave

 

Yep, first generation cars are the same. In fact, back when I used to read Car and Driver, they used to list speedometer error at 65mph for every test. It's THAT common of an issue.

 

wow that sucks so this means since its reading faster im actually adding more miles on the car then i really have on it.

 

No, if you look, the odometer reads correctly, only the speedometer is deliberately set 3-4 mph off from the factory. Mileage is not affected.

 

+1 The speedo is only adjusted in its display, not in the actual counting of miles.

 

There is a simple fix to the speedo error problem.

Simply go 4 mph faster than you intend to go.

Problem fixed!

 

Yep, elegantly simple.

 

Oh really?

Someone opens a new thread about it every week! Seriously though, the speedometer can be adjusted in the computer with NCS Expert programming software: https://www.northamericanmotoring.co...ml#post3360825

 

Yup.

https://www.northamericanmotoring.co...ter-v-gps.html

https://www.northamericanmotoring.co...can-gauge.html

https://www.northamericanmotoring.co...er-is-off.html

Dave