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How to retrofit cruise control to E34 lacking factory harness, **COMPLETE**

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Total job time: approx ten hours.

This was an experiment, I'm not an electrician but nevertheless it works.

Comments, input, tips and advice welcome and appreciated and I'll edit this as it progresses. If more pictures are required then please ask.

For anyone interested I am going to have a go at fitting cruise to an E34 that isn't pre-loomed. So that will be most 520i's and some later 525i's like mine. It would be nice to simply retro fit the factory loom but it seems this went in before the engine and dash and would be a nightmare to attempt. Therefore I have studied the cruise control wiring diagrams and have decided I am going to make my own loom and fit it in situ.

Before anyone thinks of doing the same please study the electrical diagrams and make sure you understand them fully before you do anything else. My car is a '96 525i and there may be differences in wiring.

Wiring diagrams can be found here http://www.armchair..../~dave/BMW/e34/

First thing I did was to draw out my own diagram which helped simplify the wiring and I could easily see wiring colours at a glance and I mapped the wiring in a more logical and truer to life route.


Next step was to source the bits I needed. I was lucky and found a scrap car with everything in it. That would be the cruise control ECU, actuator with bracket and control stalk. The ECU is found behind the left front footwell speaker. You need the plugs and as much of the wiring as possible is beneficial. Once you have what you need, make sure all the wiring colours correspond to your wiring diagram.


Before starting I gathered all the materials required. This was my checklist:

Reel of wire


one meter of weather proof conduit to accomodate six wiresone

tapered plastic tube (sealant/glue nozzle) wide enough to feed conduit through

masking tape for labeling wires

electrical tape

wire strippers



First things first, Disconnect battery

Remove glovebox, upper glovebox trim and metal glovebox holder

Remove left footwell speaker cover with speaker and insulation

Peel back carpet to expose wiring loom, be careful as alarm wiring is in here. I set mine off.

Drivers side glovebox or trim

Lower steering cloumn shroud

Centre console (optional*)

Carpeted consol side trim

Pedal shroud

*I removed the centre console completely as I was taking it out anyway, you may prefer to just undo it and move it back a bit or even route your wiring under the heater matrix from footwell to footwell. you could remove the stereo head unit for access to run cables behind there.




Fix the actuator in position with its bracket bolted to the power steering reservoir and place ECU in left footwell speaker cavity


I had to decide where to route my wires from the engine bay to the cabin. I chose the large rubber bung on the left hand side scuttle just under the windscreen. Removing the fusebox lid gives a little more access. I made a small hole with a watchmakers screwdriver and gradually worked up until I could get the plastic tube through. A little washing up liquid helped things along hewre. The idea is once the loom is in place, you remove the tube and the rubber bung closes tight around your cable making a weather tight seal.


Once you have the tube through far enough into the cabin you can cut off the tapered part of the nozzle and the conduit can be pushed right through.


Now take six lengths of wire (160cm each) and one at a time feed them through conduit making sure once each one is through you number each end 1 - 6 so they dont get mixed up. The picture below is similar to what you should have in the engine bay and the same in the footwell.


Position your wires where you are happy that both ends will reach their components and the conduit runs through the scuttle area. Now the tubing can be withdrawn and the rubber bung will close around your loom. Neatly route the cabling along the engine bay toward the actuator wiring. Working in the footwell, measure up, trim and connect these six wires to ECU wiring making sure the colours correspond to your diagram. As i did each one I wrote the wire colour on the corresponding wire in the engine bay. Now do the same for the actuator.


When attaching the wires for the actuator you will see a bwown/orange wire. This is the earth and I crimped on a ring conector and attached it to the earth point on the inner wing. Once all is in place it can all be tidied up with tape, conduit. No-one wants to see an untidy engine bay that looks like the cowboys have had a go.



In the right hand footwell to the right of the steering column there are a number of sockets and plugs. Look for this socket. You should have another of these with your new cruise control stalk if you cut the salvage loom far enough back.


On this socket, look for the yellow and violet wire. This is the power wire and it is live.


Make sure the car battery is disconnected

Cut this live wire, and attach it to your new stalk socket, AND add another wire which will go to the yellow/violet wire on the cruise control ECU. With this new wire you can determine the route you want your loom to take and the remaining four stalk wires will follow.


Now continue to loom and attach the remaining four wires from the stalk socket to the cruise control ECU

Fitting the stalk.

Position the stalk in the column under the wiper control stalk and route the wires neatly toward the socket



The image below shows the link into the brake circuit. The brake light switch which can be found in the Left footwell under a plastic cover has a red/blue wire coming from it. Follow this red/blue wire until you find a convenient point in the loom to break into it. This needs to be cut and another wire spliced in. This new wire now in turn gets spliced into the blue/brown wire that runs from ECU to actuator.




You should have three wires remaining from the ECU now. a black/white one and a black/brown one. Both of them will go to the cluster. And there is the earth which is orange/brown and needs a ring terminal attached and fixed to an earth point. Under the left hand carpet have a look and you will see a 10mm nut with a few brown wires going to it, this is your earth point.

Wiring ECU to instrument cluster (speed output & gear selection)

Remove the instrument cluster and the plug I was interested in was this white one. Your car may be different so beware.


Remove the white cover and look for these two wires. White/black (speed output) and brown/black (gear selection)




Splice in your two remaining wires from the cruise control ECU



It is probably a good idea to connect the battery at this point and start the car. Make sure it starts and runs as normal and you haven't up set any other wiring. You could test the central locking too.

Now the interior can be put back together but make sure everything is plugged in first and it doesn't hurt to make sure you are happy it is all tidy.


Last job: Attach actuator cable to throttle plate

Moving the air intake pipe makes this job easier. It's pretty self explainatory from the picture.


Now take your car for a test drive, select accel on the stalk and the car should maintain speed. Test the accel, decel etc and of course the deselect. The cruise should also cut out when the brakes are applied then you can test resume.

Good luck guys and please be sure to report back.

Edited by jamesf

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Well if one person gets some use out of it then this is worthwhile. More bits added tonight and will continue tomorrow

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Good work, the cruise ecu should sit in a metal cradle behind the passenger side speaker (see pic)

James - I have updated the retrofit cruise link in the 'how to guides' thread with a link to this page

For everyone else reading this, here is a link to the retrofit cruise control page http://forum.bmw5.co.uk/topic/43565-total-bmw-guide-to-retrofitting-cruise-control-e34-aug-05/page__p__585144__hl__+cruise%20+control%20+retrofit__fromsearch__1#entry585144 for reference


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Excellent work :)

How good is your German? http://www.e34.de/tips_tricks/tempomat/tempomat.pdf

I did this retrofit to my '94 525i Auto some six years ago, but had the luxury of purchasing the BMW harness designed for cars that weren't pre-wired. Some of the fitting instructions were ignored as they simply weren't necessary, like removing the steering wheel but others were as the retrofit did involve using a hammer and cold chisel on the bodywork as the document suggests! Some of the wiring is done within the fusebox with the official harness - like picking up the speed impulses and the brake light feed. The fusebox is not a place for the faint-hearted...

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Took car for a test drive yesterday and all works fine. I am delighted with this result. I hope others can gain from this

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I tried to read something out of the diagrams and they are like written in Chinese to me...

One question, what E34 are pre-loomed for the cruise control?


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Well done on doing this - I fitted the correct bits to my pre-loomed 1995 E34 but sadly it doesn't work - I guess there must be something wrong one or other of the three bits.

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Sharkfan, perhaps you could use this guide to try and diagnose yours. I would check for power at the stalk plug first of all. And then the two earths.

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I'm assuming your e34 is auto?

If so would this DIY still apply to a manual?

Yes mine is auto but the only difference is a link into the clutch switch which could be simply worked out from the wiring diagram.

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Yes mine is auto but the only difference is a link into the clutch switch which could be simply worked out from the wiring diagram.

Sound I best accuire the parts soon and give it a bash :D

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Yes mine is auto but the only difference is a link into the clutch switch which could be simply worked out from the wiring diagram.

I bridged the clutch switch plug on mine with a piece of wire so it's an easy work-around.

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