x20 pin identification with unknown harness

[frankie591]

I am in the process of making the wiring adapter for the x20-c101. I have gone through the etms for my c101 and have all the functions and wire colours.

My problem is that the harness I got with my motor is from an unknown car. I think it is e34, but as for year myself and the guy I bought it from have no idea. What should I do to make sure I am hooking things up correctly since I can't be 100% sure of wire colours?

BTW car is an '87 325is, and motor is an obd1 m52.

[nando]

you should be able to go by wire colors and gauge. the only wire color I've ever seen change was the coolant sensor (the wire you don't need) and the oil pressure switch (easy enough to find since it only has one pin on the connector)

[frankie591]

Did the pin functions change much within the e34's? Like could I just take an arbitrary e34 production year and use the etm to find which pin# does which function, then match that up to my c101 function?

[nando]

they didn't really change, no. I'd still use wire color and gauge as a guide.

[frankie591]

Like just go through an e34 etm and use the wire colours from that? Also is there a way to be sure whether I have an e34 or an e36 harness? I assume that the wiring colours would probably vary between the 3 and 5 series.

[nando]

the E34 will have the relay harness by the DME plug. the E36 will have it by the round OBD connector. also the E34 harness will have the oil level sensor wiring built in.

the wire colors are basically the same for the engine on all cars - but on the E34/E36, there are extra wires that the E30 doesn't need, that could be different based on year/model/options (auto, manual etc). that's where the confusion could come in.

basically if you can at least figure it if it's E34/E36, and you use an example X20 pinout and wire colors as a guide, then verify that each wire goes to the right connector on the harness, you should be fine.

[frankie591]

I definitely have an e34 harness then. Am I going to run into problems with the dme plug not reaching far enough into the glove box? I've heard that the e34 harness is quite a bit shorter than the e36.

Thanks for the help!

[nando]

you'll have to turn the DME the other way around (plug facing the firewall). it's a pain in the ass to be honest - I wish I'd used an E36 harness, myself. an option is to extend the harness plug but that's not easy either.

[frankie591]

Is the pita mounting the dme the other way, or is it just tough to plug the dme into the harness from the back side? I don't think getting an e36 harness is really an option for me so I'll just have to make the e34 harness work.

[etxxz]

pin#s are more important than wire colors. They may or may not match, thought they probably will. The ETM's have pin#s of every junction so go by that.