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?
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!!!
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?
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!!!
