MPG on OBC II doesn`t work

E28 technical advice asked and given! Troubleshooting, modifications and more.
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Bars-zerwick
Posts: 29
Joined: Aug 28, 2011 7:02 AM

MPG on OBC II doesn`t work

Post by Bars-zerwick »

10 years ago I`ve bought cruise control and OBC II from american 528e with manual transmission. I unstalled this kit in my european 520i with M20B20. After installation cruise and OBC started working, except average fuel consumption.
Last week I tried to find the problem. I checked my instrument cluster (instant fuel consumption works on tachom as speedo work too). I changed it to another 2 clusters. I changed the chip from european 520 to 528e, also nothing changed. I checked wires from cluster to OBC - all of them were in working condition.
When speed is 0 and I reset MPG, I see ---- km/h. When I start going, MPG shows 39.5L. If I reset MPG, when the gas pedal is off and the engine is breaking, I see 0 L/km on OBC. As soon as I touch gas or RPM become idle, I`ll see 39.5 l.
I know, that OBC receives speed data, because average speed works.
Unfortunately, I don`t have another OBC to change it and to check. But could the problem be anywhere else?
Thanks.
turbodan
Posts: 9153
Joined: Jan 09, 2007 10:19 PM

Re: MPG on OBC II doesn`t work

Post by turbodan »

I don't have the ETM in front of me but I think the signal to the OBC comes off of the back of the tach and goes to the OBC through the connections labeled BLAU and WEISS. I would check that these are connected correctly and make sure there isn't another blue connector dangling somewhere on that harness. I have seen them were there are two different ones, you may have the wrong one connected to the consumption signal output from the tach.
turbodan
Posts: 9153
Joined: Jan 09, 2007 10:19 PM

Re: MPG on OBC II doesn`t work

Post by turbodan »

Image

Looks like the connections are on the speedo, but I suspect the issue is there regardless. I can't remember if I've ever seen a connection at the Grun/Green slot. I suspect Blau/Blue.
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