13 button obc help

[Howmuchisthefish!!!]

Hey guys i have an 88 325i with the original obc and the average mpg and range does not seem to work. All it does is flash. I was hoping you guys might have an idea what to look for. Everything else seems to work like code and temp and the speed limiter. Also there is a single yellow wire plug thats not connected to anything i was woundering if this had something to do with it. If not can someone tell me where it goes?

Thanks again, Steven

[chris4891]

if the speed limiter function on the obc works properly, it means the obc is getting the correct speed signal from the cluster. from the notes i left myself when i was installing my obc, the yellow wire is not used.

sounds to me like the obc is not getting information regarding the fuel consumption. not sure the color of the wires off the top of my head, but these are the relavent pins (on the obc plug) where you might have a problem

15 - fuel tank level input
17 - fuel rate input
18 - fuel tank low level input


out of curiosity, does the mpg gauge on your cluster work? the obc takes in the same data that is used to generate the signal that drives the mpg gauge.

if neither those 2 functions on the obc nor the mpg gauge work, id guess the problem is in the gauge cluster somewhere. otherwise check for broken wires. in either case - you should get ahold of the electrical troubleshooting manuals - they are invaluable..

[fronton]

I am a similar problem but my AVG MPG also shows 5.9MPG. I'll reset it while not in motion, it blanks out and when I start moving again, 5.9mpg shows up and never moves. Would an engine swap have anything to do with it? It is an M3 so no econometer to reference. My fuel gauge works correctly.

Does it matter which of the single pins I put the green single pin connector into on the back of the cluster? there are at least 4 options but I think it is speed signal.