MPG gauge - what are the inputs?

[tdr1919]

My 86 dash display for MPG is wacky, what are the inputs that are sensed to compute the MPG? and is it all done in the dah cluster?
Thanks,
Tom

 

[toptechx6]

Usually speed, RPM and pulse width are the inputs, likely computed by the body computer (CCM) after receiving the data from the ECM and finally sent to the cluster. All just conjecture since I don't have 86 specific information, hopefully someone else will know for sure.

 

[sriat]

I have an 85 with same problem

Would love to know the answer also!

 

[warp8]

Mine went wacky in my 86. Had to replace the ECM to cure it.

 

[tdr1919]

Mine went wacky in my 86. Had to replace the ECM to cure it.

Warp8, on a different thread you were asking about the "shift light" somehow
I believe these two things are use the same information, I wonder if vacuum is also one of the factors?
Tom