My 2004 (build date 12/2003) R53 has the OBC option in the tach with speed, temp, etc...

I'm running G-Force Sport Comp 2 205/45 r17, and I've noticed the digital speedo is off by about 2mph over my actual speed.

For reference of my actual speed, I'm using my GPS and the speed radar signs on the side of the road that warn drivers how fast they are going in residential areas.

I know they aren't the most accurate, but I'm constantly seeing the 2mph difference.

Is there a way to get into the ECU and adjust the speedo value similar to how the ECU can be reset by entering test modes?

 

It's over intentionally to prevent law suits. I don't see how 2 over is an issue, just remember that it is.

 

Not really an issue, more of a minor annoyance.

It used to be 1mph difference with the Potenza RE760 tires. I was a little surprised by the difference.

 

My 05 r52 is also off by 2. Here's the funny thing. When I plug in my bluetooth OBCD2 reader the speed reported agrees with 3 GPS's. The digital readout off the car is off by 2. So it does look deliberate.

 

Interesting. I never checked it on my Bluetooth app OBD Fusion. I'll have to check it out. Thanks for the heads up.

 

It may be about tire size, wear and inflation. I've driven past those temporary radar trailers that show what speed you're going - my OBD readout has always been spot on. That's at relatively low speeds, though, like 35-40 MPH.

 

Its off a little, normal.

 

You are correct. I checked it out today using the Bluetooth adapter to my phone, and the ECU is reporting the speed correctly (off by 2mph).

It's definitely an intentional adjustment to the speedo display as stated above and had nothing to do with tire size or inflation in this case.

 

The topic comes up every week. It is adjustable through NCS Expert programming.