S2kRob

Just to make absolutely sure here, the yellow box also adjusts the odometer, right?

E30M3

Odometer measures distance traveled. Speedometer measures speed. Another way to confirm calibraton is to use a watch on the highway. Highways have accurately spaced mile markers. At 60 MPH, going one mile takes 60 seconds. 8.25 versu 8.27%? 0.02% off is nothing to worry about, few cars have truly accurate speedos. Most read a few percent higher than true speed. And when your tires wear, the accuracy changes since the tire diameter changes. Different tires and/or air pressures change the rolling radius too.

Stan

S2kRob

Yeah I know, but what I want to know is does the speedo signal feed the odometer, and is the yellow box downstream of the point where the odo picks up the signal.

xviper

The speed sensor gives the ECU the signal from the output shaft of the tranny. The ECU then tells the speedo what to say AND it calculates what the ODO should record based on that signal. The Yellow Box intercepts the signal before it reaches the ECU so the "corrected" signal will affect both the speedo and the ODO by the same amount.

S2kRob

Excellent. Yellow box here I come!