Possible BCU failure?

Just bought a 2002 Discovery 2 with engine problem with the plan to fix and use. Put a new battery on to get it on trailer, alarm went off and i disabled it no problem with remote. I locked it that night after having it running then next day would not unlock. Left battery disconnected for a while then every time it’s reconnected the alarm goes off but can’t be disarmed. Remote happened to work once and now alarm is disarmed but immobiliser won’t come off. Tried again couple night ago and remote worked once again, immobiliser light stopped flashing but still behaves as if Immobiliser is active. Light on dash started flashing again after a couple minuets. New battery in remote.
I’ve also noticed electric windows and hazard light don’t work now. The windows were working the day I picked it up and had it running.
Earths I’ve found look ok and I’ve had jump leads between battery and body to try rule out a bad earth.
I’ve had the fuse box out and looks ok. There in a tiny little bit of corrosion at the base of one pin but is hardly anything. The symbol on the dash (B with a line through it) is flashing on the dash all the time.

I spoke to a company that do recon exchange BCU’s and fuse box repairs today but they say I need to determine if it really is the BCU or fuse box before they will help. Apparently Land Rover recommend replacing the fuse board every 8 years. They also said a dealer won’t be able to determine if one or the other is faulty as they can’t test the line??? Said I have to go to an independent Land Rover specialist with the right equipment to be able to diagnose! I’m sorry but I really can’t believe a dealer can’t diagnose a land rover fault!

Is there anything I can do to test either fuse box or BCU or do I just have to try one? I’d happily test wiring if I knew what wires and pins went where.

Thanks
Ben

Any thoughts on how I could test for the faults I have? Would using the Lynx diagnostic be good enough for testing and possibly programming a replacement BCU or would it have to be nanocom?

Thanks
Ben

Have you tested fuse F23 in fuse box under steering wheel as this is used by bcu to energise starter coil relay.
Neither the bcu or idm (intelligent driver module) an integral part of the fuse box under steering wheel record or store their faults so it is impossible to test them .
To better understand them and their relationships you need to read up about them in RAVE, the D2 workshop manual where you will find under BCU a detailed description of their functions of how they control them.
If you do not have Rave look at post 12 July 2019 D2 1999 workshop manual which has links to allow you to down load them for free.

With regard to a possible replacement BCU be aware that if you look at a used one it needs to be in an unlocked state or come with synced working key fob otherwise it is useless. If you want a reconditioned one search for callrova the only people with the ability and capability to repair D2 bcu, also very helpful.

ben342w said:

The symbol on the dash (B with a line through it) is flashing on the dash all the time.

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this can be ruled out only by exclusion, first replace the interior fusebox(IDM) cos it's almost plug and play then if no joy go for the BCU... forget about those schmucks who said that you have to diagnose which is the faulty one.... plenty of info here https://www.landyzone.co.uk/search/65589361/?q=crossed+b&o=relevance&c[user][0]=9153

ben342w said:

Would using the Lynx diagnostic be good enough for testing and possibly programming a replacement BCU or would it have to be nanocom?

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if it's the ''classic' lynx it might help ...the EVO is full of sh*t

Yes, all fuses have been checked and are fine.

Spoke to the chap at Callrova just now as suggested and he was far more helpful than the last so called repair company I tied. He thinks it’s more likely that my fuse box at fault due to both front and rear windows not working and initially cased by oil reaching the red plug on the ECU from the injector wiring. I’ve cleaned the oil up but made no difference so I’ll order a new harness and get a replacement fuse box. Fingers crossed that sorts it. He did say there is a chance when the fuse box had failed it has affected the BCU but I’ll need to do the fuse box first to find out.

Might have the chance of a rotten TD5 for parts so if it’s the right age I might try getting it as a donor. It’s still being driven just now so at least I know it works!

Thanks
Ben

ben342w said:

He thinks it’s more likely that my fuse box at fault due to both front and rear windows not working and initially cased by oil reaching the red plug on the ECU from the injector wiring.

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OMG, what a claptrap ... the oil ingress in the ECU red plug has nothing to do with IDM or BCU nor with the crossed B sympytom whatsoever... though off course that the injector loom has to be replaced if it's oil there cos it can cause engine running issues

let' hope it's the IDM(interior fusebox\)... disconnect the battery before you swap it and after the reconnection turn ignition on 2 and let it so 5 minutes.

Just a thought, I had a similar fault on my td5 which had stood for a couple of years when I bought it, the fault was a poor earth on the fob receiver ( can't remember the real name) in front of the rear sunroof, cleaned up and all fine, not sure about the windows etc, mine had no switches etc fitted

Are you saying that a poor earth at the receiver triggered the crossed B on the odometer ?... if not your problem was not similar at all

Once you get the ignition on disable the immobiliser with your lynx

Currently trying to source a fuse box but seem to be struggling. All the ones I’ve seen have a different relay layout to mine. My one has 5 relay positions (3 small and 2 big) but all the ones I see have only 4 (2 small and 2 big).

Comfortablynumb said:

Just a thought, I had a similar fault on my td5 which had stood for a couple of years when I bought it, the fault was a poor earth on the fob receiver ( can't remember the real name) in front of the rear sunroof, cleaned up and all fine, not sure about the windows etc, mine had no switches etc fitted

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That was one of the first things I tried before I found out the symbols on the dash actually meant something!

Discodevon said:

Once you get the ignition on disable the immobiliser with your lynx

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The Lynx belongs to my old boss but has said if I got the TD5 disco unlock for it I could have used it. It’s currently only unlocked for the P38 Range Rover.

ben342w said:

Currently trying to source a fuse box but seem to be struggling. All the ones I’ve seen have a different relay layout to mine. My one has 5 relay positions (3 small and 2 big) but all the ones I see have only 4 (2 small and 2 big).

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That extra relay is for those which were factory set with DRLs especially scandinavian specs so as long as that DRL thing(which IMO is neglectble) isnt a big issue to you then you can buy any fusebox which was removed from same modell as yours, important is not the year but if it was facelift or not so if your's is not facelift any non-facelift fusebox is OK the same for facelift if you see what i mean.

If you can get it unlocked/started take it to someone with diagnosis who can disable it for you, I had some issues with my old disco td5 so just disabled it, ( you can still lock it on the remote) but can get to work without worrying about not being able to start it

sierrafery said:

That extra relay is for those which were factory set with DRLs especially scandinavian specs so as long as that DRL thing(which IMO is neglectble) isnt a big issue to you then you can buy any fusebox which was removed from same modell as yours, important is not the year but if it was facelift or not so if your's is not facelift any non-facelift fusebox is OK the same for facelift if you see what i mean.

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Managed to find one on eBay today that is identical to my one so I’ve bought it. Hopefully here this week to try!

Discodevon said:

If you can get it unlocked/started take it to someone with diagnosis who can disable it for you, I had some issues with my old disco td5 so just disabled it, ( you can still lock it on the remote) but can get to work without worrying about not being able to start it

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I’ll have to do that once it’s running. Need to sort the engine once I’ve got this immobiliser issue sorted out tho. Need it running so I can diagnose the problem I bought it with ‍

Well looks like the replacement fuse box has made no difference at all!! Put the ignition on position 2 after reconnecting battery for 15mins now. Still have the flashing B with line through it and all the same functions not working. Guess I’ll have to try the BCU now! Trouble is I have no way of coding it! Would I have been able to swap a BCU, ECU and keys from a non facelift model with no issues or would they still need coded?

As the IDM is ruled out the BCU is the next suspect, If you swap the whole lot BCU, ECM and fobs from other working vehicle with the same transmission and suspension then your's should run without warning lights but tester is still needed cos the mileage will flash as it doesnt match the IP so the odometer error warning must be disabled and the injector codes have to be saved in the ECM, not a proper way to sort this thing, for BCU or ECM replacement a tester is compulsory IMO.... though if your's is a late 2002 facelift or Eu3 better forget about swapping the ECM too

sierrafery said:

As the IDM is ruled out the BCU is the next suspect, If you swap the whole lot BCU, ECM and fobs from other working vehicle with the same transmission and suspension then your's should run without warning lights but tester is still needed cos the mileage will flash as it doesnt match the IP so the odometer error warning must be disabled and the injector codes have to be saved in the ECM, not a proper way to sort this thing, for BCU or ECM replacement a tester is compulsory IMO.... though if your's is a late 2002 facelift or Eu3 better forget about swapping the ECM too

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Ah perfect, thank you for your reply. This is a facelift model and the one that i can rob parts from is a non facelift so I’ll not bother going down that route. I’ll speak to callrova tomorrow and see if getting it repaired will wipe it to factory or if it will retain my coding etc so can just bolt back on essentially.
Hoping there turn around is quick as I could do with this on the road for middle of the month and still need to fix engine once it’s running again then get MOT’d!

Just an update on this issue. BCU has been away for repair and now all my faults are gone

Now to sort the engine issue... looks and sounds like a stuck injector on cylinder 1,2 or 3. One of them front three anyway. Hopefully have that sorted quick enough!

Thank you all for the help and input, it is much appreciated.

Thanks
Ben