mjojom

Hi Guys,
some time ago I battled myself through from seats retrofit. My car come with pretty good specs but one thing I was missing on my long journeys across Europe was comfort front seats. So I decided to look up some and get the pair with matching leather to the rest of the interior for about 400 quid. as soon I got them I realized this would not be an easy task and was prepared to pay someone for fitting them in. Sadly, 99% of those asked turned my idea down as near impossible to impossible. what, why? this is just damned seats! I found some garages, everybody was telling me different stories and nothing added up. Some of them wanted up to 1000 pounds to fit the seats in. ha, no way!
So I put up the laptop together with all the guides, pages, and manuals about BM electrics and components I could find. I got my mate to help me out, as my patience is limited and one thing he is really good at is to sit and try until he succeed (got him to read wiring diagrams).

I am retrofitting from leather half electric heated sport seats to comfort leather seats.

First we need to find out which fuses actually the seats are on.
in my case they were 31 and 33. thats for my seats, the original comfort ones are wired differently.
when I undo big yellow connector on the drivers side this is what it looks like:

this is power connector to the drivers seat and including K_bus cables.

the white and small black connectors are heating for base and back rest.
drivers seat does have pretensioners on both sides of the seatbelt, so this is the second wiring for it:

and this is another end of the yellow plug for original seats:

next picture is comfort seat yellow plug, you can see the wiring is slightly different:

main difference is in between Brown and Red red/green wire, which I simply run wires outside of the yellow plug and crimp the new connectors on and join them together outside of the connector.
One think, this wires should be wired to the relay in the boot, to have only power when car wakes up, but me being me, this was too far for me to run the wires to, so I just connected them as I mentioned above. this way seats does have constant power. Since retrofit car has been standing for periods longer than 2 weeks and battery was always fine so I do not see the issue there. (i retroffited them in september last year)

another important difference is, comfort seats does have additional pretensioner in back rest to react in collision and put the contour backrest to straight position.
THis must be wired with new wires green and blue was my choice 21 & 22, and thats connected to the airbag module in B pillar. For driver side the pillar is on the driver side.

One more new wire is K_bus, without which the seat would not move with controls on the side. there is K_bus module behind the glovebox compartment, but I figured out it would be easier just to track next junction and connect it there - this could be found on the PDC/DCS/SEAT heating module which is just on the center console.

the following picture is airbag module from B pillar and connector with my new green/blue wires



THe passenger floor:
this is floor connector:


and comfort seat passenger:


note with passenger seat there is same amount of new wires, but:
in yellow connector brown/black wire has to be moved so they correspond to each other on both sides of yellow connector- very easy to do.
and there are extra wires for occupancy sensor, but they are wired in just fine.



well, my seats working just fine, including memory function, however I did not code em in yet, so I got restrain system errors. this should be due to the fact that ECU`s for seats does have different functionality and safety features (one more pretensioner).

hope that could help someone and save £££`s.
I was really shocked when I found on the net that wire loom for each seat will cost me £160 to buy = £300 for both seats. Wires which I have runed myself for less than 10 quid.
it took us very long time, but we never done anything like that, and neither of us is auto electrician. I can easily say this would be no more than 1 day job. Why someone wants to charge us 800 quid and thats without wiring looms etc???

Pallokerho-35

I salute you brave sir, excellent work! Thank you for the documentation and for proving feasibility.
I'm sure this will prevent some enthusiasts' headaches in the future...

mmitev

Great work and a big Thank You for contributing this!

mjojom

you are most welcome lads. a bit shame I could not post more pictures. is that a restriction in general or because i did not post enough posts?

straba

Hi Mjojom,

I did the retrofit myself, but did not connect the active hedrests to the B-pillar modules. I also swapped the pretensioners to my original ones, so I got no safety system warnings.
I am in particular interested whether you will manage to get it coded without errors, especially the active headrests.
Please post how it goes.

Regards

bmwrider2010

awesome! this is what I was looking one thing I can't understand how many bpillar modules in the car 1 or 2? I know main module (big) is under centre console where the other 2? also I believe both seats have active headrests but you have connected only 1 seat with blue & green wires how is that work with only 1 seat connected what about other one?

bmwrider2010

Fixed! on my it was a different story because I had to plug active headrest to airbag module two pins for each seat diagram can be found on WDS. no more active headrest errors

toms206

great thread, well done, In which case, can i ask you might you know how to resolve a high resistance fault, i swapped a cloth interior for leather, plugged it all back in and get error 93F8 drivers seat, resistance to high in tensioner....? Have ask a local diagnostics person to reset but it blinks of then back on. any thoughts what can sort this issue. Wires are good, intact and corrosion free, no breaks or splits etc..... Any pointer welcome.