The following �How-to� is intended for DIY owners like me who have limited mechanical and technical knowledge. I defer humbly to our more experienced members for whom this is probably routine stuff!

For some time I had been having intermittent issues with rear door and tailgate unlocking combined with heavy steering on my 2005 Td6 Fatty. This problem (documented on this forum) can be caused by a faulty BCM/BCU (Body Control Module/Unit). I was daunted by the prospect of replacing my unit, firstly because I am no more than a reasonably-competent DIYer with no mechanical training or experience, secondly because of the cost, and lastly because I have no garage and working outside is no fun � it is often too hot down here to work in the open and, on the rare days when it�s not sunny, it�s often raining!

The new unit requires programming to the car otherwise, it seems, many features will not work (see http://www.fullfatrr.com/forum/topic33390.html, in particular Mattstevenson2005�s post d. 25/08/2015). This was what was putting me off as programming would normally have to be done at a Stealers or Indy, and I have no confidence in any near where I live. However, those wonderful chaps at GAPDiagnostics have now developed a module for the IIDTool which does the programming. Axle � who had already done it � convinced me it was really simple, so I decided to bite the bullet.

Having contacted GAP, they promised they could indeed make a special build available for my model/year to download to my IIDTool. They were true to their word!
So, I ordered a new BCM/BCU from Duckworth Parts (site sponsor).
I now had no more excuses �

In theory, replacement of the BCM is simple: remove the passenger seat, unplug the old unit and pull it out, put in the new, plug it in, run the IIDTool module � and bingo!

Unfortunately, for me, things did not go quite that smoothly and I had a few issues: silly things where if you�re in the know, it�s easy; if you don�t know � So I decided to do this �how-to� in the hope it will help other DIYers avoid the silly mistakes I made.

Down to work:
Note: My Fatty is LHD. Please bear this in mind if the images do not correspond 100% with RHD cars �

Step 1 was to download the special build provided, on request, by GAP (this replaces the standard analysis module in the IIDTool so afterwards, once you�ve finished, you need to re-download the standard module):
- Start the updater software then connect the IIDTool to the computer
- Click on Find device
- Select Special build �nnnn� (provided specially by Gap)
- Click on Program Firmware
Wait until completion, then disconnect.

Next, in the car:
Step 2 was to disconnect and remove the old BCM/BCU and replace with the new unit. RAVE suggests the front passenger seat has to be removed but I found that simply unbolting it and tilting the whole seat backwards gave plenty enough room to work:
- Move seat to fully-back position and undo the 2 seat runner front retaining nuts (16 mm). Now move the seat fully forwards and remove the 2 seat runner rear retaining bolts (also 16 mm).
- Disconnect the battery (see Wiki) and wait 20 minutes or so for all systems to shut down
- Tilt the whole seat backwards, taking care not to stretch the cable connected to the underside of the seat.
- Remove the black plastic BCM/BCU cover plate (2 �turnbuckle� screws you turn through 90�):


- Unclip the 3 multi-plug connectors:

wiki'fied Steve,  ... - .- -.




Y. O. L. O.
.

I am indeed honoured , kind Sir  It's "bébéchoon", ackcherly, with accents. 'Steve' to my chums.
20 years ownership of Solihull products, ALL GONE NOW, sniff!
Current motor: Suzuki S-Cross 4WD auto, 1.4 petrol. Oh so reliable! 7 years now and no problems. Oh, all right then, a leaking shocker replaced under guarantee.
Previous:
TD6 HSE L322 Auto FF
2.5 TDi 4-door Classic
Disco II
And my 1st Rangie: in 1995, a 2-door VM 2.5 diesel Classic
Not to mention the Lada Niva before those. (I said not to mention it!)

Superb procedure Bebechoon. Thanks for going to so much trouble to document it so thoroughly.  2006MY 4.2 SC
BMW R1250 GSA Rallye TE
Triumph Tiger 1050 (sold)
1979 Pontiac Trans Am (sold)

Bebechoon,

This is a perfect solution so thanks for posting

............but does anyone know if the Faultmate extreme can program the BCM/BCU unit?

regards

John

** EDIT **

It appears the Faultmate will program the BCU...........see you all later

This is a great post, and may end up coming in handy.

Can anyone provide a part number for the BCM/BCU for a 2012 5.0L 5000CC V8 GAS DOHC Naturally Aspirated FFRR???

This part is the most mysterious thing I've ever come across! Even the dealership quoted me (I think) the incorrect part. I asked for a part number/price on the Body Control Module/Unit and they gave me a price for a Fuse Box (LR023679).

Just to add to this thread

I found there is no need to unbolt the seat, just wind the seat to its most forward position, then from the rear footwell pull out the entire BCM (the white VHS size box, not the black plastic surround) with the cables still attached. Its then much, much much easier to remove the connectors

Best wishes
Glen

Just a thanks for including such a good level of detail. This gave me confidence to tackle the BCU on my L322 when almost everything BCU related shutdown. Main fault was BCU locked in Transport Mode. I bought the Gap IID BT Tool but although the BCU turn off Transport Mode command routine was accepted and executed the unit would not come out of Transport Mode (no matter how many battery resets). I bought a used BCU on eBay (exact same model BCU). Plugged in - selected renew BCU on Gap tool and everything immediately back up and working (so far as i can tell but main items all working).

Many thanks.

Mark
L322 Overfinch 580S

Thanks bebechoon, have to say that your post is one of the most comprehensive I've seen on any forum, I found it after a search to find how to remove the big plug from the bcu - I needed to be a bit more brutal.

The reason I was taking it out is because the passenger side rear window decided to go down and won't go up
The motor is fine and the drivers side window works ok
I disconnected the pressure sensor plug but it doesn't make any difference.
I think the relay on the board is ok, because i connected a bulb across the motor and it lights briefly when the battery is reconnected.
Pretty sure all fingers are pointing at the bcu

Anyone disagree?
Can i just replace it like bebechoon did?
Can I get one from fleebay and use that?
Would it help if I get keys with it?

I have an IID tool

Thanks

don't know what model/year you have but BCU are a straight swap (altho there are different part numbers for different years). Do you find your steering is heavy too? Can also stop the rear pax door unlocking.

2002 L322

Apears just to be the rear window at the moment. Also I note that the windows will open on command via the IID tool, but they won't close on command.

i find my steering heavy some times and the rear gate plays up some times
i can always lock me car when its parked at home but when its in a car park some where, its like wining a lottery RR 2005 4.4 petrol
Any spelling mistakes are the fault of spellchecker
Previous MG J2, CITROEN light 15 x 2 gone unfortunately
Present MERC 180e, RANGE ROVER L322, JAGUAR XJS, MERC 280SE, MG F, JAGUAR S-Type 6v 2003, jaguar s-type 8v 2004, Ford Cougar

Hi, knares (& others!)
You've described the symptoms I had (see my 2nd para right at the start of this thread) except that, for me, it was pure chance whether the locks would work at home either ...
It seems many peeps have had this intermittent problem and often it has been the BCM at fault. Fitting a new one could be the solution for you, although of course it may well be another problem ...

 It's "bébéchoon", ackcherly, with accents. 'Steve' to my chums.
20 years ownership of Solihull products, ALL GONE NOW, sniff!
Current motor: Suzuki S-Cross 4WD auto, 1.4 petrol. Oh so reliable! 7 years now and no problems. Oh, all right then, a leaking shocker replaced under guarantee.
Previous:
TD6 HSE L322 Auto FF
2.5 TDi 4-door Classic
Disco II
And my 1st Rangie: in 1995, a 2-door VM 2.5 diesel Classic
Not to mention the Lada Niva before those. (I said not to mention it!)

Tried a BCU reset
et voilà

Is the BCU reset a Hard reset, or something different? 2005 FFRR SC Java Black with Overfinch Exhaust (UK)
2008 D3 HSE Stornoway Grey (UK)
2008 D3 HSE Izmir Blue (ZA/Zimbabwe)
1995 D1 300 Tdi (Zimbabwe)