The BC1 (Body Control Unit)

86839 Views 26 Replies 12 Participants Last post by  Alski
The BC1 (Body Control Unit) is in the driver's side (UK) footwell, it controls many electrical items and can send many things haywire if even a drip of water gets into its PCB connectors until it dries out. If you pull the footwell bonnet catch lever, hold it open & shine in a torch behind the trim panel you will see the top 2 (Blue) multiway connectors to the BC1 or a black plastic cover. Early MINIs (pre-2003 approx) did not have the black plastic shield over the connectors to protect them from any small drips of water running down the cable harness inside the windscreen pillar. Later cars do, my 2002 Mini only had a piece of clear plastic film draped over the connectors (a factory or dealer stop-gap fix I guess) and was randomly locking/unlocking the central locking by itself after any rain / wet weather, washing the car, etc. I removed the inner sill plastic trim panel & fitted the later water shield cover (part no.61356942512 approx. £2) over the 2 top connector plugs.
See Diagram Item 9
If this is the problem do not ignore it as long-term corrosion inside the BC1 means a new unit with...very expensive outside warranty.
(Some people have successfully opened more badly water-damaged units, dried them out gently with a hairdryer, removed any corrosion, and got them working again).

Once BMW had discovered the fault originally, all cars (early 2002) made had plastic water-resistant film placed over the bc1 plugs while the new cover was being designed, which took a matter of only a couple of weeks.

Many of the original cars have unprotected BC1's, but this cover was intended as a precaution rather than a cure.
The actual cure was to make sure that A post finishers were fitted correctly, ensuring the clips fitted watertight.
Only cars that had ill-fitted A post finishers in the first place were affected or badly replaced trims/windscreens later.
It was a run of these that caused the original problems.

Anyone with an early car that has had no problems would indicate that the A post finisher was obviously fitted correctly preventing water from getting behind the green clips.

Below is the BC1 connections listing showing how many things it communicates with and is also a useful reference. Connections may vary a little depending on the options fitted and the year of your MINI - always double-check with the Bentley Manual wiring diagrams or BMW MINI WDS CD.

Body Control Module - Overview - MINI 2002-07
[pdf manual no longer available]

(If the BC1 is replaced with a new or secondhand unit it would normally need to be re-programmed by a BMW dealer.)

MINI Cooper BC1 connections

X332 20 pin green "A"
X253 54 pin black "B"
X254 54 pin natural "C"
X255 54 pin blue "D"

Pin-Description-Connects to/from

1 Terminal 30 Fuse F37
2 Passenger window open Passenger door window motor
3 Terminal 30 Fuse F1
4 Passenger window closed Passenger door window motor
5 Ground Chassis ground
6 Driver window open Driver door window motor
7 Terminal 30 Fuse F19
8 Driver window closed Driver door window motor
9 Left high beam Left headlight
10 Ground Chassis ground
11 Ground Chassis ground
12 (not used)
13 Right high beam Right headlight
14 Terminal 30 Fuse F14
15 Left low beam Left headlight
16 (not used)
17 Terminal 30 Fuse FL12
18 (not used)
19 Right low beam Right headlight
20 Terminal 30 Fuse FL8

Pin-Description-Connects to/from

1 Motor "ZV unit central arrest" Central locking, fuel filler cap
2 Motor "unlock trunk lid" Central locking, trunk lid/tailgate
3 Driver door unlock From X257 driver door
4 License plate light
5 "Load cutout" From glove box light
6 "Trunk lid contact" From trunk lid/tailgate
7 Interior light
8 (not used)
9 Motor "ZV unit lock driver door" To X257 driver door
10 Passenger door unlock From X256 passenger door
11 "DWA siren alarm" Antitheft alarm system horn
12 (not used)
13 (not used)
14 (not used)
15 Interior protection From "interior protection I" module
16 Interior protection supply From "interior protection I" module
17 (not used)
18 Motor "ZV unit lock" To X256 passenger door
19 Manual headlight vertical aim From headlight beam height control
20 Motor "ZV unit unlock" To X257 driver door
21 Driver door lock From X257 driver door
22 Driver door contact From X257 driver door
23 Heating blower relay
24 Trunk lid button From license plate lights
25 Luggage compartment light
26 Motor "ZV unit unlock" Central locking, fuel filler cap
27 Antitheft alarm status
28 Passenger door lock From X256 passenger door
29 Rain sensor signal
30 Tilt alarm sensor signal
31 (not used)
32 (not used)
33 (not used)
34 Drive-away protection signal Tilt monitoring
35 (not used)
36 (not used)
37 Manual headlight vertical aim From headlight beam height control
38 Motor "ZV unit unlock" To X256 passenger door
39 Rear window wiper motor
40 Front lid contact Hood closure
41 (not used)
42 Passenger door contact From X256 passenger door
43 (not used)
44 (not used)
45 NOT USA: Motor "ZV unit central arrest" Passenger door lock
46 (not used)
47 Interior light "continuous on"
48 (not used)
49 (not used)
50 (not used)
51 (not used)
52 (not used)
53 (not used)
54 (not used)

Pin-Description-Connects to/from

1 Xenons: left vertical aim motor ground Q22 Otherwise: recirculating air flap motor
2 Xenons: right vertical aim motor ground Q12 Otherwise: recirculating air flap motor
3 Xenons: right vertical aim motor supply Q21 Otherwise: recirculating air flap motor
4 Headlight washer module (negative activation)
5 Front right turn signal
6 (not used)
7 Fron right parking light
8 Rear right turn signal
9 Left auxiliary turn signal
10 Ground Connection X179
11 Front left parking light
12 Right brake light
13 Right auxiliary turn signal
14 Left brake light
15 Left rear fog light
16 Front left turn signal
17 Right rear fog light
18 Rear left turn signal
19 Right vertical aim motor Q22
20 Left vertical aim motor Q12
21 Left vertical aim motor Q12
22 Rear window defogger relay
23 Wiper motor fast/slow relay
24 Right rear side marker light
25 Right side marker light
26 (not used)
27 Terminal 30 Fuse F4
28 (not used)
29 Left tail light
30 Center brake light
31 Terminal 30 Fuel pump relay 1
32 (not used)
33 (not used)
34 (not used)
35 Brake light switch signal From connector X10197
36 Terminal R Fuse F7
37 Xenons: right vertical aim motor ground Q1 Otherwise: recirculating air flap motor
38 Left vertical aim motor Q11
39 Windshield defroster relay
40 Front fog light relay
41 (not used)
42 Right tail light
43 Rear window wiper motor relay
44 Wiper motor on/off relay
45 "ZV remote control" From central locking remote
46 Central locking remote supply To central locking remote
47 Left rear side marker light
48 Left side marker light
49 (not used)
50 (not used)
51 (not used)
52 (not used)
53 Kbus From/To connector X10116
54 (not used)

Pin-Description-Connects to/from

1 (not used)
2 Wiper switch 1 From wiper controls
3 Rear window wipe switch From wiper controls
4 Recirculating air switch From heat/ac controls
5 Front fog light switch From toggle panel
6 High beam flash switch From light controls
7 Passenger window open switch From toggle panel
8 Rear window defog switch From heat/ac controls
9 (not used)
10 (not used)
11 Headlight switch From light controls
12 (not used)
13 Recirculating air switch LED From/To?
14 Windscreen wiper LED To ?
15 Rear fog light LED To toggle panel
16 Rear window defog LED From/To? heat/ac controls
17 AC switch From heat/ac controls
18 Windshield defroster switch From heat/ac controls
19 Rear wash/wipe switch From wiper controls, connector X13661
20 (not used)
21 Front wash/wipe switch From wiper controls, connector X13662
22 Wiper switch 2 From wiper controls
23 AC switch From heat/ac controls
24 Rear fog light switch From toggle panel
25 Passenger window close switch From toggle panel
26 Windshield defroster switch From heat/ac controls
27 Parking light switch From light controls
28 Kbus signal To/From instrument cluster
29 (not used)
30 Blower control voltage To connector X15
31 (not used)
32 Left/Right turn signal switch From light controls
33 Evaporator temperature sensor
34 Xenons: recirculating air flap switch Otherwise: headlight beam height control
35 Evaporator temperature sensor
36 (not used)
37 (not used)
38 Cruise control switch From steering controls
39 (not used)
40 Driver window close switch From toggle panel
41 Driver window open switch From toggle panel
42 Centerlock switch From toggle panel
43 Hazard warning switch
44 Centerlock switch From toggle panel
45 (not used)
46 Kbus signal To/From OBC
47 (not used)
48 (not used)
49 (not used)
50 (not used)
51 (not used)
52 Xenons: recirculating air flap switch Otherwise: headlight beam height control
53 (not used)
54 (not used)

Electronics inside the BC1 Unit
Electronic engineering Computer hardware Circuit component Electronic component Passive circuit component
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wow ... your a true geek ;) :D However .... I have to say... Nice one! Thanks for all the info, could come in useful if my electrics ever go mad, which after 6 years of abuse they still haven't :lol:
Nice work. Where did you get this info from?
Fantastic work! :D Now any chance of the same for the ECU?? :D
If moisture has entered the BC1 - you can open them and dry out -slowly on warm surface and gently remove the corrosion inside ,it has worked for us before - there are still no repair alternatives other than dealer supplied new one ,and coding
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i heard BMW did try to make a few water tight by sealing them better
Nice work. Where did you get this info from?
I gathered most of the info a couple of years back (when I started getting BC1 electrical problems outside of warranty), mainly by trawling internet sources, the Bentley manual (expensive but much more comprehensive than Haynes) and the BMW Dealer WDS (Wiring Diagram System) CD's.
I like to fix most things myself if possible and find out how it works, or at least know what the dealer is going to do, especially with my MINI long out of warranty. To solve the wet BC1 they originally estimated about £500 to fit a new one and then program it.
To access the BC1 Unit:
Pull off the rubber door seal (drivers side UK) along the lower sill / doorstep, then carefully prise away the plastic trim panel along the inner sill / front footwell trim with a large scewdriver / rag to protect paintwork. In the interior photo below you can see the large round white nylon clips in the bodywork which hold the trim. If you wish to completely remove the trim some find it easier to remove the seat and lower belt mounting. (I normally manage to gain enough access without though).

Reconditioned Exchange BC1 (Body Control Module) are now available from BBA-Reman £100-150 which is a lot less than a new unit from BMW :thumbup1:

See Link Below:


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If water has got in\. whats the best way to cure it. Obsviously put the new cover on but whats the ebst way to dry it out??

Ive had some of the above problems after recently having a new windscreen?
Probably best to remove it from the car by unclipping the connectors and removing the securing bolts and then leave it in a warm place to dry out.
Hi There,

How do i fit a BC1 cover? I found this:

MINI R50 R53 One/Cooper/S body control unit BCU Cover on eBay (end time 23-Feb-10 15:37:10 GMT)

but am unsure if A) It will fit my 01 Mini One and B) how i fit it.

Looks like an earlier type of cover which will just slide over the BC1 and cables/connectors. The black hard plastic cover referred to in my original post just clips in position over the 2 top connector plugs without disconnecting any cables. (part no.61356942512 approx. £2).
See Item 9 in diagram linked below:

How to fit:
problem please help i have no ac no flasher in cluster no rear defrost no light in cluster radio write disable no power on f5 fuse driver side thanks
Does anybody know how to remove the large green plug from the bottom of the BC1 ? I've removed both top connectors/plugs (black and blue) and the bottom white plug which all have the same form of release mechanism but the larger green plug seems impossible to remove and I don't want to break anything ! I've got this far I don't want to just leave it like this, BC1 is even now unbolted from the car but still can't remove lower green plug. thanks for the guide though, great stuff so far!
hi i have a 51 reg cooper a few months ago the passenger side door would only lock and not unlock with central locking, then the head unit fuse went and i acidently took out the lock fuse and put it in the head unit fuse slot thinking it was a spare fuse, then i put a new fuse in the lock one, after that no sides would lock inc boot and only the drivers side would unlock, i tested and theres voltage to the motor plugs but no voltage when the button on the fob is pressed on any terminal. i had it plugged in on diagnostic and it showed faults on the locks, rear wiper and a few other bits, the body control unit controls both these doesnt it? thats whats making me think its the body control unit at fault. on the diagnostic the electrician could use his machine to lock and unlock the doors but it wasnt working but on his machine when he pressed dead lock doors both locks would lock, doesnt the dead lock work off a different circuit to the body control unit?i took the side panel off to access the body control unit and it has a cover over it. does this mean it will have been recalled once? tonite went to the car and now the drivers side is locking and unlocking and passenger side is locking. the passenger side still wont you think water could be still causing this? as it stopped working and now working again, maybe could have dried out. appreciate any help thanks
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problem please help i have no ac no flasher in cluster no rear defrost no light in cluster radio write disable no power on f5 fuse driver side thanks
Did you ever get this sorted? I have the same problem after I changed my gearbox on my R50 cooper! (2004) I'm so frustrated I have tried everything, new cluster, BC1 module and now believe it is a problem with the K Bus.

Can any body help me?:crying:
I just had a look at mine as when we bought the car one reciept says BC1 unit replaced. I went in search for a cover and i think there is one one but not sure. Behind the catch i can see the top of the unit with what looks like a blue cover but i am not sure if thats the case or not. Can please someone show a picture of the plastic case on theirs so i can see if this is it or not.

Useful BC1 post by 'unmmalterman' on .......thought it worth adding here in full for future reference!

Weird Electrical problems:
Hi! I'm no expert, however, my son-in-law who knows absolutely nothing about cars, has a 2003 R53 S which I sourced & bought on behalf of my daughter (nice 30th birthday present, eh!) he lives in London and was experiencing similar odd lights flashing, window dropping, etc., but mainly rear brake lights coming on after lock up, sometimes side lights, and dash going crazy.

All this drained the battery so he tried the 'local' garage who gave tales of woe and suggested the speedo had been diddled by the previous owner, the diagnostic (generic code reader) gave the fault as "serial module connection -dashboard".

(I researched THIS forum and the BC1 module mentioned by mab01uk seemed to be the culprit.) Son-in-law then took the car, at my suggestion, to a BMW main Stealer for a definitive diagnostic test...£198 charged for the hour! oops.
Together with a long list of sundry faults (not asked for) which totalled......ready?........£6,514 to fix. ha ha.

(Tip:To continue using the car, disconnect the battery earth in the boot and lock up manually, in the morning, unlock drivers door, pull the ring under back seat to open boot and re-connect battery. Irksome, but keeps you going.)

I therefore towed the mini, with my 65yr old wife, 220 miles to Lancashire and said I'll sort it. Found the mysterious BC1 box down by the drivers right foot, (easy! -undo seat belt mount/pull off trim along sill/undo 10mm nut/black box pulls off./#4 connectors from loom/loom is wrapped in daft cloth tape, which is wet, this is the cause, water leaks in via windscreen seals, down loom into BC1 and it also then sucks water up from the wet floor (capillary action). I stripped the cloth insulation off and used proper plastic ins. tape just to band the wires together.)

Now, one garage chap I mentioned this to said it's possible, maybe, to actually dry out the box using heat & hair dryer, then replace the plug in connections (which have a sort of sliding sideways action) this is a long shot but would therefore, cost you nothing if it then works ok. If not......

The next stage, without taking the module off, is to buy a replacement, on ebay used ones are around £55, I got a brand new, unused one for £120! Next it must be taken to a garage (not BMW,unless you're loaded) who specialise in re-programming such black boxes, I went to North West BMW in Horwich, Lancashire and they simply unplug then re-plug new module in, then use laptop to re-program it to your existing keys. They have to take readings from the faulty one first so DON'T UNPLUG IT YOURSELF! your keys won't work with the new module so you'd be stranded. For this they charged £65 but don't quote me on that, I think, ahem, it should have been more. (They give fantastic, honest service and really know their stuff)

Anyhoo, all done, no further problems. It seems it's an acknowledged fault on the mini and apparently the cure is to.....ready?.......wrap it up and seal it in a polythene bag. I'd suggest wrapping self-amalgamating, waterproof electrician's tape very tightly round the wire bunches and then tie-wraps around whatever polybag used, but very tight, water creeps everywhere!!

This was a big mystery to me before, and certainly scared the **** out of my daughter & sil, with hindsight, it's actually very easy.

I'm working on some of the absolutely ludicrous list from BMW as some of it's MOT stuff, which has run out. However, the original main fault was cured for £185 but could be a lot less if using a 2nd.hand module, or even nothing if you're lucky and do as I did. Good Luck. I think this is my first posting on here so hope it's clear and useful. Cheers. Tom.
Electrical Problem Please Help - MINI Cooper Forum - MINI2 Mini Cooper Forums

Brake Lights stuck on?
Maybe damp in the BC1 or a wet diode......
brake lights stuck on? - Page 5 - MINI Cooper Forum - MINI2 Mini Cooper Forums

Mini Cooper ECU replacement
"I managed to track down a seller who specialised in Mini spares and found a second hand ECU at the bargain price of £100 complete with Key, Barrel and EWS from the same vehicle. I was feeling quite pleased with myself for tracking down such a bargain and once the ECU and other bits were fitted the car ran perfectly.

Great i thought! until i got out of the car when i got home and tried to lock the car! The new key failed to lock the doors or open them for that matter once i'd locked them with the original key.

I did a quick check on the net and found a few threads with various techniques for programming keys, however none of these worked. In the end i took the car to a BMW specialist i know (Yes - should have gone here in the first place!) where he told me that when you change an ECU not only do you need the Key, Barrel and EWS from the donor car you also need the BC1 unit or Body Control which is also coded to the ECU and Key!
Luckily the company who sold me the ECU still have the BC1 from the same vehicle and are sending it out to me know.

I've since searched on Google and various forums and have not found any mention of needing the BC1 as well as the parts from a donor car. So i thought i'd post this as a warning to anyone else who needs to replace an ECU, and to see if anyone has had a similar experience of this?"
Mini Cooper ECU replacement - MINI Cooper Forum - MINI2 Mini Cooper Forums

An interesting damp BC1 case and it's solution below as recently reported on
Dashboard lights not working?
Dashboard lights not working? - MINI Cooper Forum - MINI2 Mini Cooper Forums

The General Module (BC1)
A few posts ago, I looked at the bus systems within the MINI electronics and how it lays the groundwork for the specific modules that send and receive communications along the data paths:
There is a BUS in my MINI ! - Mini Cooper Register Forum

Now its time to review the function of the General Module.

The General Module or as it is often referred to as the Body Control Module or BC-1. It is the module that manages a number of specific vehicle systems and is located behind the passenger kick panel just in front of the door.

It has two primary K-bus connections, one to the Instrument cluster and one to a network bus. This body control module is a consolidation of a number of smaller system modules that control and monitor the following systems: drive-away protection, locking systems, rain-sensing wipers, sun roof, park distance control, mirror control, audio systems, navigations system, keyless entry, power windows, xenon headlamp control using the leveling sensors, run-flat warning system, all interior lighting, and the multi-function steering wheel. The control module also manages the anti-theft alarm systems if installed and the keyless entry system and its RF receiver.

Although the K-bus is a fairly slow, it is event driven. Messages sent out by the Body Control module have the highest priority on this bus and will override other K-bus traffic . As noted in previous discussion, messages are distributed to all devices but only the specific module being addressed responds to the unique message and subsequently react. This is similar to a computer network where messages are sent to all devices, but only a specific IP address, like a printer, actually responds to the command. As seen in an earlier article here, the General Module is connected to both the K-Bus and Instrument Control Cluster, which in turn is a part of the D and DS-2 Bus infrastructure.

The General Module manages the lock/unlock functions, tailgate release, fuel filler cap and convenience opening of windows and sun-roof, when you hold the door unlock button down for more than five seconds. The drive-away protection or electronic immobilizer - referred to as EWS or Electronic Watchdog System - makes it impossible for the engine to be started by any method other than using the specific keys provided with the vehicle. This operates by matching a primary code that is programmed into a chip set, located in the vehicle's key and into the General Module. A secondary code is changed every time the vehicle is started and stored in the key each time. If they do not match, the engine management control module and the starter are disabled. The key communicates back and forth with the system by way of a transponder in the key and a ring antenna that surrounds the steering lock cylinder. If you bring the body of your key up close to the ignition switch, with the driver's door open, you can hear the familiar chime, even though the key is not in the ignition.

This drive-away protection system can support up to 10 keys for one vehicle. Only a MINI dealer can provide replacement keys and is capable of canceling the electronic authorization codes, in the event of a stolen vehicle being recovered and re-keyed using the BMW scan and diagnostic tools DISplus, GT1 or MoDiC

The General Module, is a sophisticated device capable of controlling all of the body electronics and has an integrated diagnostic system capable of reporting a number of faults to the OBD connector located in the driver's foot well. This is the connector that your MINI dealer ties into to conduct fault location and analysis and fix an ailing MINI.
(Posted by murmini on 31 December 2006)
murmini - MINI Cooper Blog : The General Module
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I have a problem with my BC1 module for my '55' Cooper S Hatchback.

Took it to a BMW / Mini specialist who quoted £530 for supply, fit and coding. I know someone who has a BC1 module from a Non S Cooper Convertible who I will be able to get the BC1 from for a good price.

My question is, will it work?

If it doesn't work, can the second hand units be re-coded?

Thanks in advance
55 is that a late R53 ? If so a second hand one can be re coded . When mine was swapped the key did not work the central locking but did start the car ,, lock it when used in the keyhole . If you find a second hand one from a car with similar spec to yours it is pretty much plug & Play apart from the central locking . That was my experience anyway .
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