Im not sure. Im guessing its in conjunction with the ECU since it also shows RPM's and trouble codes. So maybe its a more accurate... I dunno.

 

Wow? I thought everyone knew how to do this.

I set it all the time.

Here's a trick, you have to set your odometer to your tripometer (not actual miles, but miles since you last reset it) or it won't work. So start the process with your tripometer on the screen...