rob_bell

Well-Known Member
Hi guys,
I wonder whether you clever folks can help. A simple question and then the scenario:

Q: can you replace the rear fusebox/ BCU (part number LR078822) with a second hand unit - and what needs to be done to get the car to recognise it?
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The scenario:
Three months ago, after, ironically, driving home from Solihull (!), coming off the M6 and onto the M1 south, the car's dashboard erupted in multiple error messages as each of the car's ECUs appear to have been thrown off the vehicles CAN network. No gears, no nothing, but at least the engine was still running - luckily I was able to get off onto the hard shoulder, albeit in a rather dicey position on the curved flyover.
5 minutes prior to this general electrical meltdown, the ESC warning had come on - which was odd, didn't impact the general running of the car, but this was the prelude to what was to come.

After about 10 minutes sitting in the car with the ignition off, a firm push-down and hold of the start/stop button seemed to hard-reset the vehicle, the gearbox fault appeared to clear and the gear selector rotary control descended into the console and then came back out with the engine springing back to life. This reset did not last long, but fortunately long enough for me to get the car into a safer position on the side of the M1.
With all the errors returning with a vengeance, I called the AA - who brought a low-loader and took the car to the nearest service station. There, some chappie with an aftermarket diagnostic unit cleared all the faults (without reading them!!!) and the car appeared to be back to normal. Luckily, the car then completed a successful 60 mile trip back home without another fault.

I'd rather work on my own cars, but being time strapped, I booked the DS into the nearest JLR garage in Barnet the next day. Within a mile from home, the ESC fault reappeared, prefacing the subsequent flurry of electronic fault messages and again the gearbox being stuck in gear. I was able to do the "hard reset" trick with the start/stop button again in a supermarket carpark. However, once again, this re-set did not last that long - and with the gearbox, I think, stuck in second gear, I limped the DS to the dealership where it has languished ever since (big mistake, but hindsight is always 20/20)

The dealership's diagnosis was that the vehicle's rear fuse box (BCU) was at fault - and there are threads on line that would support this unit being at fault, causing problems exactly like those I have encountered. Unfortunately, it would seem that part number LR078822 is on back order (usual excuse: chip shortage etc. etc.). It is expensive, but if it means my car can be returned, that would be brilliant, but there is no sign of it all these months later.

In the meantime, I have had all the fault codes given to me, along with the fuse box/ BCU unit itself. Contacting LR itself, revealed the two pins that the CAN is connected to - although I do not have the detailed wiring diagram of the BCU itself. However, checking the circuit continuity across the two pins reveal the expected CAN terminator resistance of 120 Ohms. Nothing at all obviously wrong.

I wonder whether there is an intermittent fault with a dry solder joint, or whether the fuse box/ BCU is not actually the culprit, but rather another ECU (perhaps the ESC module, given that this is reliably the first sign of an impending electrical melt-down).

So here I am. No car, LR dealership unable to do anything as they can't replace the box they want to replace - and, of course, no real guarantee that replacing it would fix the problem.
What I would therefore like to do is replace the old BCU with a good second hand unit to see whether this resolves the issue - but with the ECUs all talking to one another, can I simply do this???

If anyone has any other bright ideas, I am all ears - please let me know!!! :)
 
There, some chappie with an aftermarket diagnostic unit cleared all the faults (without reading them!!!) and the car appeared to be back to normal.

LR and most other manufacturers don't recommend just erasing codes, as it erases all the history leading up to the failure.
Clearly a clueless mappet.
 
So here I am. No car, LR dealership unable to do anything as they can't replace the box they want to replace - and, of course, no real guarantee that replacing it would fix the problem.
What I would therefore like to do is replace the old BCU with a good second hand unit to see whether this resolves the issue - but with the ECUs all talking to one another, can I simply do this??

Do you have a copy of SDD and a Mongoose lead?
If so I suspect it's possible to do.
I used SDD to fit a second hand ECM to my FL2, and although SDD said it can't do it, I just configured the second hand ECM as though it were new, and SDD just did it without an issue.

@PRO is very knowledgeable with SDD on newer LRs, so hopefully he'll be along in a bit to help out.
 
LR and most other manufacturers don't recommend just erasing codes, as it erases all the history leading up to the failure.
Clearly a clueless mappet.
I know - he seemed shocked that I asked for the recorded error codes before admitting that he'd deleted them! For better or worse, the fault recurred as a carbon copy, and I have the full list of these, although they don't provide a clear "smoking gun" clue as to where the fault truly lies...
 
Do you have a copy of SDD and a Mongoose lead?
If so I suspect it's possible to do.
I used SDD to fit a second hand ECM to my FL2, and although SDD said it can't do it, I just configured the second hand ECM as though it were new, and SDD just did it without an issue.

@PRO is very knowledgeable with SDD on newer LRs, so hopefully he'll be along in a bit to help out.
No I don't - I may drop you a message later to find out more!

I have also sent a message to Callrova and hopefully in the new year, I will have time to get access to the car once again and see if I can get some more insight into what exactly is going on!
 
Multimeter, one probe to earth other probe to one of the can wires, expect to see 2.3/4/5 volts, then check the other can wire volts should be very close to each other.
Under 2 or over 3 suggests an issue.
I saw 1.3/6 volts on one pair of can wires, and 5v on another yesterday, 3 hours and I was none the wiser, handover!
 
Hi rob

sorry to hear of the issues mate , also wonder that as @lynall suggested with regards to the canbus, have the following test sequence and wonder by testing both high and low and then looking on a wiring diagram to see what modules are fitted

Fingers crossed it may also be of use to u


With both battery leads disconnected from the battery posts

Multimeter set to ohms, ( TP Is just short for test probe from ur multimeter)

TP to pin 6 other TP to pin 14 , read ohms ( should read around 60 Ohms)

TP to pin 3 other TP to pin 11, read ohms ( should read around 60 Ohms)

Reconnect battery, ign off , meter set to Vdc

TP to pin 6 other TP pin 4 Read dc ( should be around 2.5 Vdc

TP to pin 6 other TP to pin 5 Read Vdc

TP to pin 14 other TP to pin 4 Read dc ( should be around 2.5 Vdc

TP to pin 14 other TP to pin 5 Read Vdc
 
sorry if you’ve already seen these , alas don’t know if it’s possible by pulling fuses from the rear fuse box that go to various modules and then retesting the canbus to see if it will re turn to 60 ohms

hopefully there of some use to u , fingers u get it fixed mate and isn’t a nightmare

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@gstuart - brilliant! I did get some limited information from Land Rover themselves, but this information is super helpful!

Hope you're keeping well mate - and Happy New Year! :)
 
I had, thanks - the question I have not been able to get answered is whether the car will accept this "new" module - the dealership says no, but then they would say that wouldn't they?

no probs mate ,

ur right there with regards to dealers , never forget they told me it’s impossible to retrofit cruise control to a FL1 TD4 , as we all know it was plug and play with second hand modules, lol, of course understand it’s a different story with the DS , know it would be a £100 experiment to at least try to see if it works

shame with a multimeter hooked up to ur OBD2 socket showing the 120 ohms if u couldn’t move the wiring looms going to and from the rear fuse box to see if it changes to 60 ohms

what year and engine is ur DS plse as might be able to find something in some of the links etc I’ve got , thks

Fingers crossed for u mate
 

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