Pasted from another forum:
I woudn't recommend you do this on the road, you may also permanently damage your car. Do NOT do what I describe below!
>Turn ignition on
>Hold down the trip reset button on the side of the speed readout display (I didn't know it was there until someone told me about this technique).
>A menu will pop up at the the bottom of the speedo screen
>Short press of the trip reset button will move you through the options
>One will be 'Dyno test' or something like that
>Long hold on 'Dyno' option until the next screen pops up asking you to confirm
>Short press of the button and you will get lots of warnings!
>ABS is disabled, traction disabled, engine regeneration is disabled
>Spin those wheels!
To reset just turn off car and lock, when you unlock all will be back to normal. I assume this mode is available to allow running of the car on a DYNO to test BHP etc. Running a modern car on a DYNo where just one set of wheels spins, with ABS/Traction systems can send those computers nuts and throw up all kinds of errors.