golfnutintib

One of my 964's has the onboard computer in the tach. Cool feature.

All functions (range, speed, etc etc) work fine except the fuel consumption calculation. It is permanently stuck on a certain number, never changes.

I can use the control lever to reset it but the same static reading just reappears.

Any thoughts on how to troubleshoot and correct?

Spyerx

is the range accurate from your perspective? Maybe you're very consistent in your driving style? :-)

I just looked at the wiring diagram, hell to follow, but looks like it has inputs from: fuel pump, speed, load, fuel level, maybe a few other sensors. Either the OBC computer is bad or one of the inputs is not sending right. Seems expensive + pointless to fix. Possibly cheaper to swap the face and remove the stalk :-)

golfnutintib

thx for replying chris

no it is not accurate at all... it is stuck at '9.5 mpg' constantly... after resetting it just comes back at that figure, never changes

funny that other items work fine like speed, fuel range etc etc etc, just not mpg - i think if there is a fuel pump sensor that must be it, but i have also read that the computer module has a little memory chip that can go bad

agree with you its not worth fixing... just the OCD in me getting the better of me

ToreB

This is most probably due to a failing internal component in the tachometer. Indeed fixable, and not especially expensive.
The tank, speed and engine load (Tn) signals are probably OK since you have normal readings in the other modes.
Cheers,
Tore