V50 AWD problem Topic is solved

[fuzzyblacksheep]

Greetings! looking for ideas in diagnosing my 2010 V50 (Rdesign AWD M66 trans). I do appologize if someone saw this same post in Volvospeed, but I wanted to crosspost into the centre of repair knowledge as well as some of the techies over there, in advance, please forgive my faux pas.

But anyway

I've reached a bit of a dead end, I'm scouring the forums for additional info but wanted to also put out a request in case there was new or additional knowledge.

Anti-Skid service required on accompanied by BLIS service required (odd, eh?)
Vida codes for communication drop out

Changed- Fluid(looked clear), Pump (was still functioning), Filter (not too clogged), had shop remove and send DEM out for rebuild, even with all this still the exact code.

Monitored live data feed on VIDA: Pump current is around 1A, never exceeding 1.5ish on load dropping down off load, pressure varies normally but no comparison data to ID, idle pressure and off pressure spot on, Temp sensor reported a believable number but did not confirm.

Monitored Steering angle and all believable values, monitored yaw and accel, all believable (not sure what tolerance is but I would assume that these would throw their own codes.), only other codes are an occasional wiper sensor code, BLIS sometimes says service required but it's infrequent and nothing logged in vida, and had one clutch sensor code from a few drive cycles ago, nothing concrete or related to the main AWD codes.

Here's where it gets tricky, the reported velocity for the DEM is garbage compared to indicated velocity AND BCM reported velocity, when going 40KM/H, the BCM reports 40KM/H and the DEM reports 70KM/H, and this discrepancy exists across the range. Not sure where it gets this info, how it's parced or anything of that sort to compare against, hoping someone had some data on this correlation.

Furthermore, even after it throws the communication code there's no interruption in data received by VIDA, it never actually disconnects. It just throws the code and continues to transmit but I loose AWD.

Assuming the DEM velocity discrepancy isn't a set workaround or within tolerance, my running hypothesis is that the DEM velocity read out is garbage and during sometime in the drive cycle (maybe load dependent or something) it compares these values between the BCM and the DEM and when it determines the DEM values to be garbage, it considers the DEM to be damaged and junks it throwing the light and code. With no hard details, however it's almost impossible to confirm or deny (this was passed on to the shop it's at, however, and they're going to see if they can find out something about it). Beyond this, I'm at a loss.

Shop is looking at it again since they recommended DEM rebuild and it wasn't the problem, but probing for some info on my own to aid in the process.

[MadeInJapan]

Good luck. I don't know what to tell you. Are any of the tire sizes different from each other? Not that this would throw those codes, but if a spare were used or one tire's tread is gone but others are okay for instance, maybe the car senses the speed difference in rotation and somehow feeds this to the computer turning the AWD off and sending you the odd message? Anyway, that's the only thing that comes to mind to me but I know very little about the AWD system in these later Volvo's. My S40 with AWD (same M66 trans) is new to me since Feb last year- before that, all of our Volvo's have been FWD.

[fuzzyblacksheep]

They were bad at one point but the first thing I did even before getting the aoc pump and filter was brand new tires all around and a fresh alignment. No dice. Some bushings are worn but nothing is torn or floppy. It's kind of driving me batty

[MadeInJapan]

Sounds like it! You might try a full "reset" of the system...disconnect battery (key out) wait at least 5 mins and touch the negative and positive battery cables together, put everything back and restart your car... might or might not help but seems that some kind of code is stored which is causing your issues even after an original problem has been resolved.

[fuzzyblacksheep]

The problem was far more simple. I was all ready to get out the multimeter and begin checking everything but the shop it was at checked the one thing I didn't think to check, their own work. They changed the pressure sensor as a precaution but they installed the wrong part number sensor by accident. Womp. They swapped it back and no lights!! Thanks for y'alls help!

[MadeInJapan]

Glad it was that simple and they figured it out!!