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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > Looking for VO code for electric OEM tow bar



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      07-20-2021, 03:37 AM   #111
Bean801
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Quote:
Originally Posted by Andystobbs View Post
For the AHM wiring I'll need some info from you. The different versions have different Pinouts.

Can you find which pin numbers your Red/violet and Red/yellow wires go to in the AHM plug and report back.
I have managed to have a look at the plug today.
Its super hot and as i've now got COVID just getting this info has turned me into a huge sweaty mess.
But the pins are
The Red/Violet wire goes to pin 13

The Red/Yellow wire goes to pin 20

While i was in the boot i noticed this
https://share.icloud.com/photos/0SYL...RViDnEEpySCGCw
Can i connect the twisted green & green/orange wires here?
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      07-20-2021, 04:21 AM   #112
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OK so after crawling around and dismantling everything I have found out why my tow hitch isn't releasing, but I will come on to that - let's see if we can get your wiring sorted and get you up and running with yours.

If we deal with the Earths first of all - you should have 3 thick brown wires coming through the boot grommet from the exterior part of the loom - here is my loom from the grommet spread out (ignore the thick blue wire in the picture)



Plus one thin brown wire coming from each of the 2 modules (AHM and AHV), and all 5 of these should terminate on the earthing post in the boot pictured here:



This is on the E90 at least, the earthing post may be somewhere different in the boot on the E91.

So with these 5 earth cables terminated, and the various coloured wires going to their respective modules, the rest of the loom travels up to the front of the car. You can see in my picture the additional thick Red/Violet cable that I ran to the fusebox at the front of the car, in case I have to update to the newer AHM at some point which expects two +12v feeds.

For the AHV hitch release module, here is a picture of my 16 pin connector showing the pin numbers and you can hopefully make out the colours of the cables that should be present (ignore the Yellow/Black cable in pin 16, this was present in my connector but isn't used as it was for the old speaker on pre 09/2006 cars that sounded when the trailer hitch was released)





For the Trailer lighting module AHM, here is my 16 pin connector - bearing in mind my car is a 2011 and some of the pins changed on this module depending on year, but this should get you most of the way there and we can figure out what is different on your setup





So those pictures and information combined with Andy's pin information should hopefully let you make some progress
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      07-20-2021, 06:14 AM   #113
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Quote:
Originally Posted by Andystobbs View Post
Pin 12 White/Brown is tailgate contact switch, you'll find this at the tailgate lights.
This enables the operation of the towbar when tailgate is open.


Looking at the wiring diagram this goes to X465. Do you have an image of where this would be & what it looks like?

Is it just a live feed when the tail gate is open. From the tailgate courtesy light?
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      07-20-2021, 06:44 AM   #114
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That White with Brown trace wire is an Earthing signal from the tailgate when its open. You should be able to find it if you find where the tailgate / bootlid wiring loom comes into the car, and tap into it. All of the boot compartment lights use the same earthing circuit so you should be able to tap into a White/Brown cable going to a boot light.

Sorry to hear about the covid 😒 hope you feel better soon!
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      07-24-2021, 01:37 PM   #115
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Finally started to feel normal again and as the temperature has been much better today for working in i've been and had a go at the wiring for the tow bar.

There are a couple of wires that i have connected but not sure if they are in the right place

1st one is black with yellow trace from the AHM module. - In the retro fit guide it says to connect it to the footwell module, pin 40 of cable of same colour.
I have connected it to pin 40 but the cable colour there is not the same its a blue with brown trace. Does this mean its in the wrong place or just that the wire colours have changed over the years?

2nd one is blue with brown trace from the AHM module. - In the retro fit guide it says to check weather signal 49HR is applied on the BL/BR wire of the vehicle wiring harness. I dont know what this means but i have connected it to the wire of the same colour on the rear RH light cluster.

Result.........

It works

The tow bar deploys & retracts as it should.

I haven't yet been able to borrow a trailer or caravan to test if the electrics for the lights are working but everything else on the car still works & i haven't got any warning lights so fingers crossed they are also working.

Regarding the coding, i have a local auto electrics near to me that can do the coding. What does the coding actually do? Is it worth having it done?

Thank you all for your help & assistance it has been greatly appreciated.

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      07-25-2021, 08:54 AM   #116
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Congrats on getting it working

It was worth it in the end! I think you can get trailer connector testers from various places, if you wanted to check the FRM connections are all correct etc before it gets to the time when you need to tow.

Regarding your wiring questions - I would double check that you have definitely tapped into pin 40 of X14260 on the footrest module - it sounds like you may have tapped into pin 40 of X14261 by mistake, which is right next to it. That would make sense why the wire colour you have tapped into is Blue / Brown - as I believe pin p40 on X14261 is Blue / Brown.



The second point about the Blue / Brown wire you have tapped into on your rear light cluster - signal 49HR is the indicator signal, so that sounds like you have done things correctly there. Hooking it up to a trailer tester or similar will confirm.

Regarding the coding, if you are going to be towing a caravan or trailer then it is definitely worth doing. The coding will tell the car when you have something plugged into the 13 pin trailer connector, and will disable your rear PDC - as otherwise, with a caravan or trailer on tow so close to the rear bumper, the PDC sensors would be constantly beeping.
The coding will also disable the cars rear cluster fog lights and reverse lights when towing, so that the caravan or trailer lights will be used instead.

Well done again on persevering, especially after Covid!
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      07-25-2021, 09:19 AM   #117
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Regarding my hitch failing to deploy and the flashing red button LED, it turns out that the centre pin which is pulled out by the motor has been struggling to move due to water ingress and corrosion
I checked all the electrical connections and signals and 12v was getting sent to the motor, so I had to remove the bumper and rear crash bar to investigate why the motor wasn't releasing the hitch. I could hear a faint motor sound as if it was trying to work.

Upon removal of the motor from the crash bar, a ton of water poured out from the plastic motor housing















The seal between the 2 plastic motor housing halves was squashed and broken in places, so I think this is one place where the water has got in.
Also, the rubber O-ring on the metal shaft of the pin is very thin and perhaps worn, which could have let water into the housing from the hitch side





The centre pin with the T shaped end is extremely difficult to move, so water must have got down around the shaft internally, which is why the motor was struggling to pull against the T shaped piece to release the hitch arm. I'm surprised it didn't blow a fuse trying to shift it.

So now I have to figure out if the motor still works and can be cleaned up/repaired, if there is any water in the reduction gear housing, if the microswitch still works, and whether or not I can somehow get the centre pin out to clean it up and remove the rust. Then whether I can get a replacement O-ring the correct size, and then look at using silicone sealer around the plastic motor housing to prevent this happening again.

For the amount of water ingress, I can only think that maybe back last year or even the year before, I had to drive through some flood water, nothing that was very concerning but may have created enough of a deluge to get past the seals and it has then just sat in the motor housing with nowhere for it to drain from.

Looking at the part number for the motor itself, 71606784797, it looks like they redesigned it a bit after my version was made originally, and the newer versions have a much larger rubber seal where the wiring enters the motor housing, so perhaps water ingress was something that was reported and so they changed design.



A new motor unit is around £125 plus postage so that's a last resort....
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      07-26-2021, 01:50 PM   #118
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Quote:
Originally Posted by Scoff123 View Post
Congrats on getting it working

It was worth it in the end! I think you can get trailer connector testers from various places, if you wanted to check the FRM connections are all correct etc before it gets to the time when you need to tow.

Regarding your wiring questions - I would double check that you have definitely tapped into pin 40 of X14260 on the footrest module - it sounds like you may have tapped into pin 40 of X14261 by mistake, which is right next to it. That would make sense why the wire colour you have tapped into is Blue / Brown - as I believe pin p40 on X14261 is Blue / Brown.



The second point about the Blue / Brown wire you have tapped into on your rear light cluster - signal 49HR is the indicator signal, so that sounds like you have done things correctly there. Hooking it up to a trailer tester or similar will confirm.

Regarding the coding, if you are going to be towing a caravan or trailer then it is definitely worth doing. The coding will tell the car when you have something plugged into the 13 pin trailer connector, and will disable your rear PDC - as otherwise, with a caravan or trailer on tow so close to the rear bumper, the PDC sensors would be constantly beeping.
The coding will also disable the cars rear cluster fog lights and reverse lights when towing, so that the caravan or trailer lights will be used instead.

Well done again on persevering, especially after Covid!
I have had another look at the footwell module today and you are quite right. There is another plug with the same amount of pins directly above the one i tapped into and pin 40 has the correct colour wire coming from it. I have correct this and all is still well.
I have ordered a trailer plug tester from ebay so will be able to test the lights prior to hooking a caravan up.

Thanks again for all your assistance with this, it is hugely appreciated.

Last edited by Bean801; 07-27-2021 at 09:49 AM..
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      07-29-2021, 02:06 PM   #119
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Quote:
Originally Posted by Andystobbs View Post
Could anyone with the towbar help me out with ordering a replacement label for the left luggage cover in the boot of my E91. Now I've fitted the towbar I'd like to add the towbar insignia/pictogram on the left luggage cover. I can't find a part number for the label showing first aid kit, warning triangle and towbar. Could some kind person pop theirs out and get the number from the back.
Also as the new label is wider I'm concerned that the clips may be further apart possibly meaning it won't fit. So if any one can measure the clips too that'd be great. Thanks
Hi, just wondering if you found the part no. for the badge? Would like to change mine if I can find one.
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      08-02-2021, 01:19 PM   #120
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My tow bar socket tester came today. Unfortunately the only pins that appear to be working are the earth & the permanent live.
No lights at all.

Is there any way to test the module to see the fault lies there?

I was wondering if the can bus wires i tapped into in front of the fuse box were the correct ones? The were 2 sets of twisted wires the same colour. Would it matted which pair i joined upto?
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      08-03-2021, 11:10 AM   #121
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Hi, that sounds a bit odd - hopefully the tester is OK and not faulty. In terms of the canbus wires, as long as the correct colour was joined to the respective colour on the car, it shouldn't matter which set of canbus wires you tap into. It may be worth checking continuity between the various 13 pin socket terminals on the BMW trailer socket, and the respective wires on the AHM module connector, to ensure they are wired correctly and there are no breaks/corrosion causing issues. I know with INPA/ISTA you can activate each lighting circuit for the trailer AHM module to check it's functioning ok, but I think you said you don't have any diagnostics software etc?
Have you had the coding done yet?
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      08-04-2021, 03:11 AM   #122
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Quote:
Originally Posted by Scoff123 View Post
Hi, that sounds a bit odd - hopefully the tester is OK and not faulty. In terms of the canbus wires, as long as the correct colour was joined to the respective colour on the car, it shouldn't matter which set of canbus wires you tap into. It may be worth checking continuity between the various 13 pin socket terminals on the BMW trailer socket, and the respective wires on the AHM module connector, to ensure they are wired correctly and there are no breaks/corrosion causing issues. I know with INPA/ISTA you can activate each lighting circuit for the trailer AHM module to check it's functioning ok, but I think you said you don't have any diagnostics software etc?
Have you had the coding done yet?
Thanks for the reply.
I don't have any diagnostic software to check that way. And i was holding off on the coding until i knew everything was working as it should do.
I will do a continuity check on the wires to the socket at the weekend and double check the can bus just in case i've had a stupid moment.
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      08-04-2021, 03:30 AM   #123
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No problem. I think given the mechanical side of the hitch release works and the electrics to that module are obviously ok, it's probably not worth doing the continuity checks etc - just arrange to get the coding done next. If the car isn't aware that the AHM module which controls the trailer lighting is fitted, then that module won't be 'live' as such and wont be sending the various lighting signals to the trailer connector. Once the relevant coding has been done, this will bring the trailer module to life and you will get the brake, tail and indicator lights etc all working
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      09-20-2021, 02:32 PM   #124
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I finally got around to having the coding done at the weekend and am pleased to report that everything is now working as BMW intended.

Thank you to everyone that helped me along the way, I donít think Iíd have got it sorted without you.

All I need now to complete the factory look is the badge with the tow bar on for the trunk cover.
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      09-20-2021, 04:43 PM   #125
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Quote:
Originally Posted by Bean801 View Post
I finally got around to having the coding done at the weekend and am pleased to report that everything is now working as BMW intended.

Thank you to everyone that helped me along the way, I donít think Iíd have got it sorted without you.

All I need now to complete the factory look is the badge with the tow bar on for the trunk cover.
Still looking for that 2 years later.
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