BMW Motronic Wiring

[Cabrio_Simon]

I've recently made a start on sorting the wiring out and, in particular, patching the BMW Motronic wiring into the Marlin loom....

It all seems to make sense apart from one wire that according to the BMW wiring diagram goes to the on-board computer and is for 'ASC and Anti-Theft (DWA)'?? Since my donor didn't have ASC I'm assuming that this wire is for the engine immobiliser that is built into the dashboard computer unit. Does anyone happen to know wether this wire is needed and, if so, is it earthed, +12V or something else?

Even though starting the engine is still a good few months away it would be handy to know what to do with it!

Thanks

Simon

[pdm_engineer]

Re: BMW Motronic Wiring

Simon
I don't recognise this wire at the moment, probably becase yours is from a 5 series as I recall, is that correct?
Can you trace this wire to either the large engine plug pin number or ECU pin number then I may be able to help. Wire colour may help as well

[Cabrio_Simon]

Re: BMW Motronic Wiring

Hello Peter,
Yes the engine/loom/ECU is from an '89 525i. Although alot of the colour coding is different, most of the wiring on the engine connector is similar to that shown on the (3 series) wiring spreadsheet you sent me.

The wire in question is black/violet and goes to ECU pin 38 and large engine plug pin 8 (the wiring diagram shows it going to OBC pin #24). The wire to pin 8 on your spreadsheet is yellow/white and goes to pin 25 on your ECU and shown as not used - did your donor car have the BMW dash computer/immobiliser?

Thanks in advance for any help you can give!

[pdm_engineer]

Re: BMW Motronic Wiring

Simon
Sorry but none of my 3 series info details what this is for.
My parts wre removed for me by FAB Recycling and I don't know whever the car had an OBC or not, all I had to go on was a bunch of wires!
I remember looking into my engine plug pin 8 wiring and failed to find what it was for. There is something on it which comes from ECU pin 25 in my case, and is probably a speed or RPM signal for the OBC to use for calculating the average speed or MPG. As it's probably an input for the OBC you won't need to use it.
My advice is to leave it unconnected, as I have with mine, but insulated. Do not wire to 12V or ground.
I don't think it will prevent your engine from running normally.
All the best Peter

[Cabrio_Simon]

Re: BMW Motronic Wiring

Peter

Thanks for the advice and I agree that the best bet is to leave it unconnected and try starting without it.

Looking at one of the BMW forums it seems that you can easily upgrade an E34 BMW that just has the dash mounted clock by simply replacing it with an OBC (apparently all cars have the wiring for the OBC fitted as standard) - so I would think its fair to assume that the car doesn't neccesarily need the OBC to be able to run.

I think the appropriate phrase is 'suck it and see'!!

Thanks again - Simon