molinero78

My name is Jorge.

From 4 weeks ago, I´m the owner of a nice 964 C4 year 92. My car has on-board computer all functions working properly, except the autonomy, always indicate 999 km.

maybe you can help me, since I´m completed lost.. any point to check

I appreciate your support

Regards and thanks in advance

Jorge

molinero78

I apreciate if some one of you can support me. My OBC mark always 999 km of autonomy
Regard

crg53

I think it's your choice of the word "autonomy", it does not make sense. Do you mean "odometer", that would make a lot more sense.

vagluv

I'm taking that to mean distance to empty.

ToreB

And I thought it was my lack of english language skills that fooled me...
I guess the tachometer does not receive the tank signal, is your fuel gauge working properly? It could also be a faulty Load Signal from the engine management unit that makes the tacho able to determine the fuel consumption. It could also be a faulty memory chip in the tachometer.
Cheers,
Tore

molinero78

Thanks for you comments
Exaclty I want to say the distance to empty, always indicate 999 km.
Yes the fuel gauge is working property. I understand that inside the tank must be some sensor to send the signal to OBC, do you know where I can find?

Regards and thanks

Jorge

molinero78

hi

Nobady can support me?

Regards

jorge

Goughary

I think you have stumped the entirety of rennlist. This is the first of this issue I have ever heard of...

In fact, I had no idea our cars had any indication of miles to empty.

Help us understand. How did you come across the problem, and what have you tried already to find a solution. This way maybe we can check things off the list...

molinero78

Here a pictures.
Always indicate the OBC 999 km or 620 miles

hockenheimr

Mine has the same computer option....but it works...that's all I can say about that

Good luck!

hepkat63

hmm, very odd. Have you disconnected the battery - leave it disconnected for say half hour, try again?
Have you read the manual? Maybe there is a way to reset this?
Does your fuel gauge read correctly?
I never use mine, but last time I looked, it worked ok.

molinero78

Yes is very odd.
Sure I disconnected the battery, still the same issue.
In the manual nothnig about this
the fuel gauge works property.

Is there inside the tank a sensor to measure this? or some mechanism that send the signal to the OBC

Regards

C24FUN

My educated guess on the operation of this feature is the OBC compares (remaining fuel)/(current consumption rate) and comes up with (km to empty). I don't know if the OBC uses the calculated fuel economy (ltr/100km) that it calculates separately or some other fuel usage measurement but I am pretty sure that there is no separate sensor in the fuel tank for this. I have not seen this problem on my OBC so I don't have much more to add. Does your fuel economy display number make sense?

ToreB

The tacho contains a EEPROM memory that can fail. This may well be the case here, especially if the tank signal is OK. The tachometer OBC computer may be having problems reading/writing from/to the memory, thus the faulty display reading.
You could try the instrument in a different 964 or 993 with OBC, and see if the instrument behaves better there. If not, you have to get your OBC fixed.
Cheers,
Tore

JasonAndreas

Any idea of what type of MCU the tach is using and/or do you have any front & back pictures of the pcb?