Speed Sensor / Wiring Diagram question

[LondonMike]

Hi Guys

I'm new to the forum, I have a '95 M5 that I am about to wire an Alpine Sat Nav unit into. One of the connections I need to make is to the Speed Sensor, specifically connect to VSS (Digital or Analogue 0V - 3V)

I know the wire runs in the main bundle to the back and into the boot and also carries the EDC wiring. What I need to know is what colour the wire is and where the best place is to intercept it.

Does anyone happen to know the speed sensor wire colour, or maybe have a wiring diagram showing the colours?

Thanks :)

[Javier]

Have no M5 drawings for 1995. Only up to 93. This info is from E34 drawings for 1995, as there are no exceptions for M5, guess they apply also.

Vehicle Speed sensor is wired between terminals 8 and 10 of X271 (12 pins gray) at the instrument cluster. 10 is wired with brown and 8 with brown/red.

There is a processed Vehicle Speed signal that the instrument cluster sends to various control modules, it is in terminal 18 of connector X502 (26 pins black) wired in black/white. Don’t know if it's digital or analogue, nor the burden capacity. Messing with it may interfere with operation of other instruments (IHKR, DME, cruise control, OBC, GM, EDC, and Radio, all of them wired in black/white), you may try it though.

Javier

[LondonMike]

Thanks for the reply Javier. I need to make the connection at the back of the car, in the boot/under back seat area. I'll try and trace the wires back. What I could really do with is the colour of the wires as they come into the car from the speed sensor, so I can pick them up before they go forward to the OBC

[Dan in NZ]

The original stereo wiring harness has a speed sensor wire, it's black with white stripe. You could also get this same wire from the OBC.

[LondonMike]

I thought it was black and white on the earlier wiring harnesses, then was changed for the later cars? The problem I have is that all of the equipment is being fitted in the boot, I really need to be able to pick this wire up where it first comes into the car which I think is in the boot too.

[Javier]

a processed speed signal, not the speed sensor. It goes to the General Module (In the LH side of the rear seat, pin 11 of X253 (26 pins, green). This pictures should help identify it.

http://www.bimmernut.com/~billr/images/rear%20fuses.jpg (http://www.bimmernut.com/~billr/images/rear%20fuses.jpg)

http://www.bimmer.info/forum/attachment.php?attachmentid=692&stc=1

My concern would be that, if the input impedance of the new device is too low, it would draw down the signal, and interfere with the rest of the systems. I doubt this could happen though, as the designer of the device should have taken this into account being an aftermarket intended device. If this signal works, it is a better one to use than the speed sensor. This signal is referenced to ground.

Javier

[LondonMike]

Thank you very very much Javier, that is hugely useful :)

I had a quick look (it's dark now) and see it's under the main plug-in blocks and requires the whole cradle removing. I'll do it tomorrow and try, do you happen to know the colour of the wire?

[Javier]

May be you can catch it in the harness coming from the dash, then with a continuity test, you can confirm is the one going to the said terminal at the GM, all without having to disassemble the rear fuse box. There is a splice (X429) joining 4 black/white wires together (those we are talking about), in the harness riding in front of the Rear Fuse box, towards the battery, and the center console between the front seats.

Javier

[LondonMike]

Thank you Javier, it worked :D

I pulled the wiring cradle out then unclipped the green plug from underneath, then unhinged the clip so the wiring and contacts came out, then spliced the nav to the black and white. While I was there I found a big black relay that was lying next to the cradle, it fits on the end of the cradle so I re-fitted it. No idea what it does as I didn't have anything that wasn't working, I'll see what new functionality springs to life...

I have been trying to get this question answered for 2 weeks, you're the first guy who has bothered to check it out for me, It's much appreciated :)

[Javier]

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