Thinning out wiring harness

[TZANIDO777]

Hey guys, so Im building my 135 into a track car and I am up to the part of thinning out my wiring harness of everything that is not necessary. This is not for weight savings although it will shed some weight, I am doing it more for cleaning up the clutter of wires that are now exposed. I have searched for about a week now with no luck on this topic, few threads about it with the M3 guys and older model BMW's but nothing for the 135.

If anyone has any suggestions/advice on things not to remove from the wiring harness in order to keep the car happy, it would be greatly appreciated. I am okay with lights on the dash so long as the car is working fine.

Also, if anyone has a wiring diagram for this car, I have looked everywhere and cant seem to find anything and there is no Bentley manual that I know of for this car yet either. Thanks in advance.

[6MT_Addict]

Originally Posted by TZANIDO777

Hey guys, so Im building my 135 into a track car and I am up to the part of thinning out my wiring harness of everything that is not necessary. This is not for weight savings although it will shed some weight, I am doing it more for cleaning up the clutter of wires that are now exposed. I have searched for about a week now with no luck on this topic, few threads about it with the M3 guys and older model BMW's but nothing for the 135.

If anyone has any suggestions/advice on things not to remove from the wiring harness in order to keep the car happy, it would be greatly appreciated. I am okay with lights on the dash so long as the car is working fine.

Also, if anyone has a wiring diagram for this car, I have looked everywhere and cant seem to find anything and there is no Bentley manual that I know of for this car yet either. Thanks in advance.

I'm not sure I understand your intent fully here; the factory wiring is very clean to begin with. It's bundled and taped quite neatly.

I've got years of experience working with electrical systems and my advice would be to leave the wiring intact and remove only the modules or components. Ie remove the bluetooth module, or remove the radio and components.

Pulling pins, especially on cars so reliant on electrical systems as ours, probably won't end well unless you are extremely thorough. If you've pulled something and now have harnesses loose, I would just tape the end to seal it from any moisture/dust and zip tie it back to something. IMO, it's not worth the time and headache to remove all the unused wiring/harnesses, especially if you remove something tied into another system by accident.

[TZANIDO777]

Originally Posted by 1AddictsAnonymous

I'm not sure I understand your intent fully here; the factory wiring is very clean to begin with. It's bundled and taped quite neatly.

I've got years of experience working with electrical systems and my advice would be to leave the wiring intact and remove only the modules or components. Ie remove the bluetooth module, or remove the radio and components.

Pulling pins, especially on cars so reliant on electrical systems as ours, probably won't end well unless you are extremely thorough. If you've pulled something and now have harnesses loose, I would just tape the end to seal it from any moisture/dust and zip tie it back to something. IMO, it's not worth the time and headache to remove all the unused wiring/harnesses, especially if you remove something tied into another system by accident.

I was thinking the same thing, did not want to mess with depinning anything with the risk of messing something up.

I guess what I wanted to ask was if I disconnect the bluetooth, comfort access, speaker, etc modules, will I have any issues with the car running or any weird lights on the dash? Are there any modules in the car that I should not unplug?

I hear you on not messing with the wiring but I want to at least unplug what I dont need and ziptie the loose wiring out of the way.

[6MT_Addict]

Originally Posted by TZANIDO777

I was thinking the same thing, did not want to mess with depinning anything with the risk of messing something up.

I guess what I wanted to ask was if I disconnect the bluetooth, comfort access, speaker, etc modules, will I have any issues with the car running or any weird lights on the dash? Are there any modules in the car that I should not unplug?

I hear you on not messing with the wiring but I want to at least unplug what I dont need and ziptie the loose wiring out of the way.

Totally, I get you on dumping the excess lol.

I don't think you'll run into any issues with auxiliary stuff like Bluetooth but comfort access might cause some issues with starting the vehicle, like a security fail safe. I'm speculating though, I would expect that you can just put the fob in the dash like on every car without CA. I don't know enough about how the system works to say with any certainty though.

[TZANIDO777]

Originally Posted by 1AddictsAnonymous

Totally, I get you on dumping the excess lol.

I don't think you'll run into any issues with auxiliary stuff like Bluetooth but comfort access might cause some issues with starting the vehicle, like a security fail safe. I'm speculating though, I would expect that you can just put the fob in the dash like on every car without CA. I don't know enough about how the system works to say with any certainty though.

Got it lol thanks for the help, much appreciated ...hopefully someone else can chime in who has gone a little more in depth with the electrical system on our cars.

[tracer bullet]

One thing I've "heard" (yeah, i know how unreliable that tends to be) is that if you need to get work done on the car, and it includes any "coding", that there will be error messages for anything removed, not just messages that can be dismissed but to a point where the coding can't be performed. Or perhaps that only pertains to a software / firmware update?

I haven't had an issue myself, and don't know the details, but for what it's worth this is told to me by someone with first hand experience with this kind of issue. I just don't know exactly what it was they were trying to do at the time.

Seems like if you pull things one by one you'll know if something needs to go back in place. Just keep the stuff on hand in case it does need to be plugged back in at some point - or for being able to resell the car someday if for no other reason.

[TZANIDO777]

So far I have unplugged Bluetooth module, comfort access module, radio, SRS module, all the airbags, speakers, amplifier and of course the seats. I am not going to unplug anything engine related.

Battery is dead cause the car has been sitting since January so have not gotten a chance to turn it on to see if anything has gone wrong. Still have all the modules so I van easily start plugging stuff back in to trace the problem.

[6MT_Addict]

Tracers post jogged my memory and gave me an idea; you could try coding out options in your VO and see if that eliminated any errors, SRS warnings excluded lol

[TZANIDO777]

Originally Posted by 1AddictsAnonymous

Tracers post jogged my memory and gave me an idea; you could try coding out options in your VO and see if that eliminated any errors, SRS warnings excluded lol

The SRS warnings I'm not worried about cause I already had them coded out when I installed my bucket seats...as far as coding goes I'm trying to do my HW and research on how to code this car and what software to use. I coded my F15 X5 myself after reading how to's on the forums and it wasn't too bad at all just doesn't use the same software as far as I know.

[The Wind Breezes]

Here are my tips for this:

--Once the car is fully stripped it's possible to trace nearly any wires with a little effort

--Take your time and make absolutely sure you don't cut or damage other wires when dealing with large bundles. Be certain you're cutting the correct wire.

--You don't need a wiring diagram if you spend a little time with the car and have even the most basic electrical knowldege, but it won't hurt you

--Once you take out all the controllers with big harnesses connected, you can usually strip the loom and get a surprising amount of wiring out just by pulling on / following the controller cable bundles.

--Take the extra time to remove anything that will make working on the wiring bundles more difficult. It's really worth your while

[TZANIDO777]

Thanks for the advice, not sure how I feel about de-pinning anything just yet. The whole car is stripped with every panel removed except for the top half of the dash so cable management should not be a problem. I am more concerned about unplugging certain modules that will cause the ecu to possibly go crazy and not allow the car to function properly.

I am not doing this for the weight savings as the tops you will save is maybe 15 lbs with a huge risk of doing more harm than good.