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2006 L322 4.2 SC HDC and Transmission Fault

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I have a 2006 L322 4.2 Supercharged that has been pretty much fault free for the last 3.5 years of ownership. It has done 63 000 miles.

About 2 weeks ago shortly after start up the dash display flashed up 'Transmission Fault' then something like 'limited gear selection' and 'Suspension Lowering', the warning dash light and traction control dash light then remained on. I switched the car off and re-started, after which the car was fine.

The next day the car flashed up 'HDC Fault' and the Suspension Lowering', again when turned off and back on the fault cleared.

Over the last 2 weeks the car has registered these same faults almost everytime its been driven (about 15 times), usually its just the HDC warning that flashed up but sometimes it flashes the Transmission warning and on occasions it has flashed up both warning one after the other.

I have taken it to a Land Rover specialist who ran a diagnostic check and could only get 'Module BUS' or similar, they said the ECU didn't seem to be talking to a module properly? They did a hard reset (what ever that means) but the faults persist.

I have replaced the battery yesterday (with a BOSCH 019 830Amp) but the car still flashed up HDC about 30 mins into my journey back from the garage.

There doesn't seem to be any pattern to the fault warnings - sometimes its within a minute of start up, other times its 40 mins into a journey cruising at 50MPH on the motorway (roadworks).

I have considered the following may be linked to the problem -

Car had an LPG conversion 2 days prior to these faults starting to occurr, this involved the battery being disconnected for 3 days and also the air compressor being moved from the spare wheel compartment, although not disconnected or anything and the faults don't seem to coincide with the air suspension being operated.

Car always sinks to its bump stops overnight, although it has done this for the last year or so (I intend to get this repaired in the near future)

Side bars were fitted day prior to the faults starting, although they simply bolted on and didn't involve anything being disconnected or anything

My thoughts/questions are -

Why did the diagnostic check simply show up 'Module BUS'

Is the LPG conversion likely to be the cause and if so in what way could an LPG conversion cause these faults

The old battery was the original one supplied with the car but when tested it came back 'Good Battery 87% charge' (I replaced it anyway just in case) - could it be something to do with the alternator, if so how would I check this?

What else could it be?

Is there anything I can do myself to try and diagnose the cause without sending it to the dealers who will no doubt want a few hundred quid to look at it!

Sorry for the long post but I wanted to put as much info in as poss.

Thanks in advance!

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  • 2 months later...


i am having the Exact same problems!!!!!!!!! it's uncanny!My 56 plate 4.2 s/c has 43k miles.

the day i picked it up from having it converted to LPG i had exactly the same problems as you.

this was only last week and we are still trying to resolve the issues.

have you had any luck?

Kind regards

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JP, I did indeed get to the bottom of this problem and you will be pleased to know that it is actually pretty straight forward (ish)!

On my car the fault was caused by the LPG installers having spliced into the CAN BUS wiring just behind the OBD plug in point (under your right knee as you sit in driver's seat). This had upset the very sensitive CAN BUS system on the RR and so the answer was to disconnect the two wires that had been spliced into the car's original wiring and repair the wiring so that the car didn't know it had ever been spliced into. Since I had this done I have had no probs with any faults flashing up.

It is easy to check if your installers have spliced into the system, just remove the side panel of the dash by your right knee and have a look to see if the wiring is original.

However, the only problem is that those two wires were supposed to monitor and adjust the fuel trims to stop your engine warning light being triggered by the trims going slightly outside the car's parameters.

My LPG installer's are still working on an alternative fix for this issue and it looks like the best option is to try and tune the LPG fuel settings to such a fine degree that the trims don't exceed the parameters.

I may have got the technical bits wrong but the above is my understanding of the situation.

I'll email you my contact number in case you need further info.

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I did get to the bottom of it, pretty simple, it was two wires from the LPG ECU that had been spliced into the CAN BUS wiring behind the OBD plug in point.

I'll email you my contact number so I can explain properly.

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  • 6 months later...


Have the exact issue as well, accept I have a 06 plate HSE, and not an LPG conversion

The first problem I have though which is different is that recently, before the faults appeared, it had been sticking in low gears - not changing up till about 4.5k revs - which must be putting a lot of over reving on the gear box, it only seems to do it from 1st to 2nd or 2nd to 3rd - not any of the higher gears, if I use the sport mode, I can change up manually - which to me shows it isn't a gearbox problem...(perhaps) more a clutch or throttle cable issue? Told Landrover but typically never failed when they test drove it - so couldn't identify a problem.

Now yesterday, whilst out on a long drive, it started to stick at low speed again, and then suddenly on the motorway we got the "transmission fault" light, HDC, and suspension lowering warnings come up. So poodled up the M3 at 50 on lowered supension, until we could come off. We then turned everything off and waited 5 mins, by which everything seemed fine, then again after about 10mins, same thing happened. Second time we managed to get all the way home with no errors.

Now, having just replaced the whole supension kit in the car and new brakes and dif seal etc, (loads of money!) I really don't want to turn up to Landrover (mum with 3 young kids) and have them give me a long list of things that need doing(and £££££ to do it), just because the faults came up etc. So if anyone knows what the gear sticking problem may be, without having to get a whole new gearbox etc, I would be very happy.

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  • 10 years later...

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