lord gary Powell
Member Since: 05 Dec 2015
Location: windsor
Posts: 4
  
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| fault code U0122 lost communication with vdc |
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Had a vehicle into day for decommissioning,
Vehicle has been retired early as its been unreliable, mainly due to suspension faults where the vehicle has a full set of christmas tree lights on the dash and suspension locks in lowest position.
so we get ,
lots of U0122, lost communications with vehicle dynamic computer. to include,
transfer box,
range select
handbrake (important this bit)
F on dash but small gear symbols on dash
airbag light on
red park brake light
amber cornering symbol
and a few others i cant remember.
An important bit is a handbrake message which shows a handbrake failure but the handbrake can be turned on if ignition key removed. This is a good clue.
If you clear all the codes they come back instantly. But you need to check the times the fault is recorded.
To do this remove the battery in the approved way and join the battery leads together to discharge bcm memory. Please remove the battery then you wont be daft and short out the battery. If battery is removed the leads will reach each other. This will clear the memory date and time.
while battery out you might aswell check all the connections behind the battery. Good practice as water always gets in or the wires break at the pins. This is not part of this problem though.
Refit battery and ignition on, lots of lights and faults again.
check for fault codes and if they are now current date and time, this points towards a power failure instead of can bus failure.
Power failure is a well documented problem, with many pointing towards the positve wire splices in the drivers side footwell.
This is a common problem, but in this case being able to activate the handbrake with ignition off points towards a loss of Negative feed.
In this particular case the fault was a failed negative connection at the body earth bolt in the engine bay, drivers side, next to the brake servo. Its behind the brake pipes but can be easily seen.
The nut was misaligned when installed and this prevented it being tightend correctly allowing the 2 black negative cables to work loose, if they were ever tightend in the first place.
Sorry for not supplying photos but no cameras allowed at work.
so we now have a perfect d3, 159k but full service history. all new brakes, front arms, front airbags, just had timimg belts and new tyres. But due to its usage its off to the crusher.
I will try my best to buy it though.
Sorry this is a bit longwinded, hopes it helps someone .
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 7th Jun 2021 7:39 pm |
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jenseneverest
Member Since: 12 Jun 2017
Location: somewhere
Posts: 769
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would be total waste to crush that, nice write up 
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| 7th Jun 2021 9:18 pm |
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