The BC1 (Body Control Unit)

[Mab01uk]

The BC1 (Body Control Unit) is in the drivers 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 MINI's (pre 2003 approx) did not have the black plastic shield over the connectors to protect them from any small drips of water running down 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 as long term corrosion inside the BC1 means a new unit.....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 water tight.
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 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.
(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
Connectors:
X332 20 pin green "A"
X253 54 pin black "B"
X254 54 pin natural "C"
X255 54 pin blue "D"

X332
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

X253
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)

X254
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)

X255
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

[R53mcs]

wow ... your a true geek 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

[Bhozar]

Nice work. Where did you get this info from?

[MINI-Morgan]

Fantastic work! Now any chance of the same for the ECU??

[MINIMANIAUK]

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

[Ant FR]

i heard BMW did try to make a few water tight by sealing them better

[Mab01uk]

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.

[Mab01uk]

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

See Link Below:
http://www.bba-reman.com/catalogue/D...edProduct=1414

[Tom M]

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?

[scraggles]

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.