Member Since: 29 Oct 2010
Location: Centurion
Posts: 94
What does this error mean? U0122
Hi Guys
What does this error mean? "U0122 Lost Communication With Vehicle Dynamics Control Module" Where is the Vehcile Dynamics Control Module? How can i test this? Where is this thing situated in the vechicle? What does it do?
Thanks
Craig2005 Discovery 3 V8 SE
BFG All Terrains
SERIOUSLY upgraded the interior boot lighting
Double flush done
25th Mar 2011 10:45 am
BBS SPY Site Sponsor
Member Since: 15 Jun 2007
Location: Sunny Cyprus
Posts: 3054
The Vehicle Dynamics Control Module Is what was traditionally referred to as the ABS (Anti Lock Braking) module. The Hydraulic Pump and Valve Block with attached Electronics unit (ECU) mounted on the Pass side inner wing (RHD vehicles).
The U0122 code simply means that BUS communications from the rest of the vehicle is/was temporarily lost and if it is an intermittent / historic code, then its nothing to worry about croucher, it happens to most ECU's as any owner of one of our systems will tell you.
Since i have a full glass, half an hour to kill and a bit of knowledge / passion for this technology i will explain further for the benefit of anyone interested to learn more.
This might seem like just a posh name sake change but it is really not. Bosch changed the name of their their then current system from ABS 5.7 to DSC 5.7 overnight.
ABS as everyone knows, is simply Anti skid control produced via prevention of individual wheel(s) rotating at any speed less than they should be during braking, which is determined by comparison of a measurement of all the wheels rotation speeds. This was done by the addition of valves that prevented the pressure being applied by the drivers foot reaching particular wheels. Each wheel also has a release valve
But this is now but one function of a system that has typically grown step by step to now also do things like:
Traction Control, which is simply the prevention of wheels rotating more than they should be under acceleration
HDC, which is simply the prevention of any wheel rotating above a set speed
These additional functions have been around a while and although useful, they were very primitive using only switch inputs to determine the difference between braking and accelerating and so on. It is really the development by Bosch, in conjunction with one of the major German manufacturers of Dynamic stability Control technology that has vastly revolutionized things.
I vaguely recall reading once that after fitting this technology, this manufacturers percentage of vehicles involved in accidents was so reduced that the other German Manufacturers went to court and successfully won access rights to the technology and there was even a Government web site set up to extol its virtues.
This technology is of course fitted to almost all vehicles including the the Discovery 3.
The technology hinges on four aspects :
1) A very sensitive Yaw rate sensor bolted directly to the vehicles floorpan on a specially created platform in about as central a position as possible.
This can be seen here in this picture
Click image to enlarge
This sensor proves very fast real time information on the angle and attitude of the vehicle as well as the G forces being applied to it in any direction.
2) A steering angle sensor mounted on the steering column that provides very fast information on what the driver is doing steering wise.
3) Fast BUS based information from the Gearbox and Engine management and other ECU's which can reciprocally be controlled over the same BUS if required.
4) It also has the original wheel speed information for all 4 wheels but of course now much more precise and it even calculates the rolling mass of each wheel based on CCF information.
Accordingly the stability control system has a full overview in very fast real time of exactly what is going on with the vehicle, not only if, but exactly how hard you are braking, accelerating or cornering.
It has a pre programmed safety envelope and after calculating the best course of action required to keep a vehicle within it under any circumstance, it will deploy any output means at its disposal to keep the vehicle from loosing control.
Once you appreciate this, the term "Vehicle Dynamics Control Module", over just "ABS" makes a bit more sense.
On a personal note:
Although i understand the technology involved and have a deep respect and passion for it, quite recently i was involved in an indecent where i have absolutely no doubt it saved my life.
25th Mar 2011 4:09 pm
Frans@yamorna
Member Since: 20 Jan 2010
Location: Tzaneen
Posts: 109
Thanks Colin,
Very interesting I am glad that technology saved you,that is the purpose of it:thumbsup:
Keep up the good work
Frans
25th Mar 2011 8:18 pm
crocher
Member Since: 29 Oct 2010
Location: Centurion
Posts: 94
WOW BBS SPY thank you very much for an excellent, very insightfull and comprehensive answer.
I took pleasure in reading it and increasing my knowledge of this topic. This function is a superb invention and was a giant leap forward in vehcile technology.
I will inspect all of the componenets involved in terms of loose connectors and dirty connections.
Thank you
Craig. 2005 Discovery 3 V8 SE
BFG All Terrains
SERIOUSLY upgraded the interior boot lighting
Double flush done
26th Mar 2011 5:45 am
BBS SPY Site Sponsor
Member Since: 15 Jun 2007
Location: Sunny Cyprus
Posts: 3054
Thanks Guys
I have a particular penchant for learning and understanding everything i can about such technology as this and love to share knowledge about what i have learned, especially when i think the technology is rather cool, interesting for others to learn about and praise worthy.
Yea Frans, i was pretty glad myself.
Like an idiot, i was traveling way too fast in an open top car with the roof down on a side road i knew well. To my amazement an Articulated Lorry, hauling a 40 foot container, pulled out of a left hand a side road, totally blocking both mine and the oncoming lane at about a 45 degree angle.
With less than 30 feet or less to go at about 70 MPH on a road strewn with loose gravel, as the junction was just being widened, I stood hard on the brakes, yanked the steering wheel hard over to the left, as the only free space was my side of the left hand turning the Artic just pulled out of, but at 90 degrees off my present trajectory and at the speed i was traveling, it really was a last hope.
All i could see was the side of the Artic getting closer, and filling my entire field of vision. Worst still it looked like my efforts to avoid a collision meant i would probably hit it sideways, my side first, and just as i was bracing myself for the impact of slamming into the side of the Artic at 50mph at least, My vehicle and it's stability Control system somehow sorted out the utter mess i had got myself into and by some miracle found the traction i needed and made the turn with even a few feet to spare !!!
As stated, I have absolutely no doubt at all that as corny as it sounds, this technology almost certainly saved my ass on that day.
Still needed a change of underpants though
It's one thing to appreciate and understand the technology, but it's quite something different when you genuinely believe you have tested it out though
croucher
I have experienced a number of cases where Communications over the CAN Bus wire pair, which is usually twisted, have been affected by their not being well twisted just prior to their connection to an ECU. A section that is untwisted of even a couple of CM can cause problems.
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I am glad that technology saved you,that is the purpose of it:thumbsup:
