Anti-skid service required

[David737]

Many thanks paddy74

[David737]

Well VIDA came up with the following:

BCM-0094 Communication between control units communication problems with DEM.

CEM-1A64 Communication with AOC control module signal missing.

When I get home this weekend I’ll have a look underneath at the rear diff and try some fault finding.

[David737]

Eventually managed time to check out the DEM attached to the rear diff. Power to the DEM is okay; 2 Earth, one 13-14v power and 2 signals (2.3v and 2.8v approx). I checked the pump by connecting direct to a small 12v battery; it sounded fine with a constant speed. It’s internal resistance was 1.7ohms. After starting the engine the pump current initially seen to rise up to approximately 8A and cycle before dropping to zero with corresponding changes in oil pressure. After just 3-5 seconds something trips and the “anti skid service required” comes on and pump current drops to 9mA with no oil pressure.
Jacked all 4 wheels of the car up and when put in to D and only the front wheels turned.
So I tried to remove the DEM however I can only undo the top bolt. The bottom is seized with evidence of corrosion in that area: the Torx head has lost its shape so is ineffective.
So I’m thinking the DEM needs repairing but I’m a bit stuck trying to remove it. Any advice welcome!

[100K+]

Originally Posted by David737

So I’m thinking the DEM needs repairing but I’m a bit stuck trying to remove it. Any advice welcome!

I have the same fault codes currently on my V70 AWD and I'm 90% sure that the fault is in the DEM. I'm considering sending the DEM to Lucus @ volvodiagnostics in London. He sorteded a DEM issue on my car 4-5 yrs ago. From what I've read the two code you have are DEM related - usually due to water ingress into the electronics in side. The fact your fastenings are corroded suggests the unit could have been compromised as many people do not have corroded bolts, and thus working DEM.

Have also read issue could be with BCM and an earth???? but not sure about that.

When I try to read the dem with VIDA its greyed out which to me is fairly conclusive proof issue is the DEM.

Re stuck bolt - try heat tapping with a hammer, and forcing bigger torx in to hole - its a 4 or 5mm "Allen" btw not torx. I also make DIY release fluid.. 50/50 vol. mix of ATF fluid and acetone( nail varnish remover - works for me better than WD40) You might also get a small nut extractor in there too 3/8" drive not 1/2"

Cheers
Bob

[David737]

Thanks Bob
My bad....it looked like a torx but I didn’t have my glasses on! Will try with an Allen key. I’ve got penetration spray and will keep using that a few times before I have another go at the bolts.
In the meantime I’ve looked at Vida again which has changed the fault codes since I took the connections off and did my testing. The following are what it’s telling me now:

BCM-0095 Communication between control units communication problems with DEM.

DEM-0006 Pump Faulty signal.

Pump still works though when powered from 12v supply.
Any ideas at the cost of repairs from Lucas or does it depend on amount of work required.
Cheers

[100K+]

OK where to start....I'm not an expert what I learned was some 6+ years ago when my DEM went bad. But... DEM-0006 usually means a pump fault. However, you say yours works.
Why/how does it work yet has a fault code??
My suggestion would be perhaps the code DEM-006 is the result of the BCM-0095???

That would be my starting point. To me the fault lies in the DEM or the pump.

Even if the pump did not work with a 12v direct supply, I think I would still want to prove the DEM was sound ( based on the BCM-0095 code) before I had to rip the car up to get to the pump to replace it. OK you have a bit of an issue getting the DEM out, but i think its nothing compared to removing the exhaust + propshaft to get access to remove the pump for replacement. ( Its the only way and you know the shaft bolts and pump bolts are going to be cruddy ) I'd be to take away if I had changed the pump ( might as well do the filter too while you are in there) with all the work involved then had to come back to do the DEM later on. The cost of proving the DEM was reasonable but because mine was broke and needed replacing Lucus didnt charge. The replacement /referb DEM unit was about £ 330 incl vat. which I though reasonable. There are other places who undertake this sort of work but I know who I trust.

Good luck keep us informed of how you go.

Cheers Bob

ps check this out as a work through - its a USA site but I find it interesting -

http://xemodex.com/us/pdf/DEM%20Flow...rt%2005-10.pdf

[David737]

Thanks Bob
Apart from checking the voltage at fuse #23 on the REM I’ve done the flow diagram and checked voltages and earths at connectors A&B and ran the pump directly using a small 12v battery.....so it looks like a DEM fault.
This all started after driving through some flooded roads so water ingress in to the DEM looks likely. Will try to remove and contact Lukas at Volvo diagnostics for a quote
Cheers

[100K+]

Originally Posted by David737

Well VIDA came up with the following:

BCM-0094 Communication between control units communication problems with DEM.

CEM-1A64 Communication with AOC control module signal missing.

When I get home this weekend I’ll have a look underneath at the rear diff and try some fault finding.

Ok. Today decided to try and resolve above fault codes on my car. Checked power at fuse 17 in the REM - ok
Checked the Blue/red supply to DEM - 14.3v
Checked the brown DEM earth - ok
Removed pump leads and connected 12v supply - pump running.
Disconnected car battery - 60ohms on white + green DEM wire. (CAN)
Decided to re-check fault codes with VIDA, and low and behold without "read all / clear all" the above codes + "anti skid service required" message had gone.
Took the car for a 10 mile run to check it out and thus far its clear. My only suggestion for the fault is poor connection of the plug in the DEM due to corrosion which my poking around with test leads/paper clips has removed.
Will see how long it lasts .. but what a lucky man.

Cheers
Bob

[lindsok]

Hello David
Did you get your antiskid resolved by replacing the DEM, my garage is saying mine needs replaced, failure of communication by DEM on my xc70.

[Parknest]

I've got the same issue with the same fault codes (ABS 0094 & CEM 1A64) as @David737 and it seems that my suspicions that the DEM is the problem could be right. I've yet to check the pins on the connector but I can hear power getting through which rules out a power supply problem.