Does anyone know how to measure tachometer accuracy?

[hrach1]

you know you could fix this whole issue with the right coding plug, right? E28 M5 AFAIK.

a regular 6 cylinder coding plug doesn't work because the scale of the tach face is different on the M3.

Ok, I purchased a E28 M5 coding plug and the RPM stil shows about 500 rev higher. :(
But at least we know now that it doesn't work! :)

[nando]

has to be a euro E28 m5?

[hrach1]

Really? What is the difference?

[Gregs///M]

Dead or near dead Si board batteries WILL affect tachometer accuracy so be sure those batteries in your SI board are fresh before attempting any troubleshooting. GL

[hrach1]

I agree but I think I have changed the so board couple of years ago. Also, the tachometer does not act erratic. It is acting normally as it is suppose to.

[hrach1]

has to be a euro E28 m5?

What is the difference between the Euro and US E28 M5 tachometer?