OBDII - Speed signal & cruise control?

[BlackSpeed66]

Getting close to finally firing up the s52 in my car. Working on some of the harness stuff behind the dash and noticed something strange. Tried to do some searching on the VSS & speed signal the new DME needs but couldn't really find a good answer.

The picture below is the factory DME harness before I began disassembly. The brown/red wire coming out the side of the harness appears to be for the speed signal to the DME. I confirmed that it did terminate at pin 29 on the e30 DME connector. The blue/yellow wire appears to be a feed from the cruise control at the back of the cluster. The ETM does list wires in these colors but doesn't actually specify they connect to each other it seems.



The "green plug" behind the dash. I did a continuity test from the blue/yellow wire on the glovebox side and it does go to the cluster (as I suspected).



I'm wondering since this blue/yellow wire was connected to what appears to be a speed signal on the original e30 DME harness.... if it is possible to use this wire as a feed for the new harness?

[luckysnafu]

Yes, you are correct. You can connect a wire from the green plug on the back of the cluster to the VSS signal input the S52 DME is looking for. You can do this via the C101 to X20 connection or directly from the back of the cluster. See related info in the thread below:

http://www.r3vlimited.com/board/showpost.php?p=3720808&postcount=30

See my sig for wiring diagrams

[mpowerful]

I did a harness for a friend in an 87is this weekend. I tapped the bu/yl wire for speed signal off of the plug for the cruise. On the etm for his the br/red goes to obc pin 26. Br/red also should be the color coming directly from the cluster. I confirmed that on his but chose the cruise wire cause it was easier to get to. Does yours have obc? What exact year and model? Hopefully this sheds some light haha.

[mpowerful]

I should also add in his car those wires never connected.. in fact in the etm the speed signal wire to the dme was listed with a caption above it saying "not used".

[mpowerful]

Hmm looking at at the first pic is that your c104? The c104 colors in his car were black(rpm), gr/red (unknown), yellow (fuel econ).

[BlackSpeed66]

Yep the first pic has the c104 in it. I did see the "not used" notification for the speed signal to the DME in the ETM. That's part of what prompted me to start this thread - since it's obviously being used for something.

The car is an '87 325is - Full OBC, factory cruise - all working fine. In my research I haven't seen a wiring set up like this and I'm wondering if it's unique to early models with cruise. Either way it looks like I can use the blue/yellow wire that's already coming from the back of the cluster over to the glove box as the feed for the speed signal, since it appears that's how it was being used before.

[mpowerful]

Im curious to know if your red and brown wire goes to the obc? Anyway i think you are on track using blue/yel for speed signal.