'06 XC90 No AWD after a few minutes of driving.
 

Hi Everyone,

I have a '06 XC90, the AWD drive is causing me a bit of an issue. I'm trying to diagnose the problem and find the best way forward. I don't really want to shell out a load of cash on anything unnecessary :confused-smiley-013:

Car drives fine, although it does take a little while for AWD to kick in. But after a few minutes, I get the orange triangle and 'Anti Skid Service Required'.

Stop the car, turn the engine off and on again. AWD works for another few minutes then the same message.

Plugged the car into VIDA:
BCM-0095 Communication between control units Communication problems with DEM (New Fault)
DEM-0006 Pump Faulty Signal (New Fault)
DEM-0007 Hydraulic pressure Faulty value (always been there and I think this is why AWD takes a second or so to kick in rather than being instant)

It might just be a coincidence but, just before the problems started I accidentally drained the battery completely flat and had to jump start the car using another car.

Have driven the car loads since but it doesn't seem to be getting a full charge, 11.7V. 14.4v when the car is running...

Anyways, I checked all the fuses with a multimeter, all good.
Disconnected the Haldex pump, checked resistance 3oms.
Connected it back up, started the engine, revved the car up a bit, back under and the pump seems to be working (it's making a noise)

VIDA seems to be able to connect to the DEM, I can see readouts from the pressure sensor etc...

I'm unsure where to go from here. Are there any more tests I can do? to see if its a fully pump/DEM/wiring?

Any info would be a great help!

Thanks

Richard

I had awd issue back in 2016 you need to be methodical and look at the clues. You have help inthat you have VIDA.

1) Check battery is giving correct voltage. Volvo hate low voltage - many electrical issues stem from an low voltage battery. Can you swap it tem pro with another??
2) Checking ( by substitution) the haldex pressure switch is much easier than checking the pump. I did however disconnect my pump and directly connected a 9volt radio battery. I ran my pump both ways for upto 10-20 secs without issue. You can hear it working.
3) Have you recently changed haldex fluid - if you have not its worth it for maintenence purposes anyway. It will give an insight into the inner workings of the unit. My oil was minging and full of crud.
4) There is a ohm test to do on the DEM unit with the battery disconnected, but at present I can't find which pins you connect and what the reading should be. If I can find it out I'll let you know.
5) There may be a water ingress issue with the actual DEM unit and the fault codes you have are a symptom of the issue of water ingress. Lucus@ Volvodiagnostics has a very good record of repairs - he's knowledgeable and helpful. hes in the traders section of the site - look him out.

Cheers
Bob

Do the same codes consistently return after they have been cleared and an updated read of the car has been done?

Thanks for your reply,

The same code appears each and every time after clearing them off in VIDA.

Thanks for this,

I've been thinking about replacing the battery for a little while now because, to be honest, I have had some wired intermittent faults with the radio and parking sensors, glow plugs...

I think it is worth giving the Haldex a service, I'm at 130k miles now.

Is there any way of testing the DEM unit easily? It looks like it's quite straightforward to remove it.

How would I go about checking the pressure switch?

Thanks again

Richard

Definitely change the battery as suggested as that needs doing regardless.
If you click on each code in the Initial State tab then view information, Vida will give a more detailed description of the code, its circumstances and possible causes.
The list isn't exhaustive but is always a good starting point to start ticking off.
You can also get live data (Parameters) in Diagnostics >Vehicle Communication then click on the relevant module.

check out5 my post 21 here :-
https://www.volvoforums.org.uk/showt...nnected&page=3

Gives a bit more info re dem

Dem & pressure switch can't be tested by "us" Thats why I suggested Lucus. As you say DEM is easy to remove ( if x2 bolts are not seized solid - metal bolts into aluminium casting) and send it off to him If its fault free IIRC cost is under £50. which you can soon spend chasing your type of fault.

Cheers
Bob

Thanks for your replies.

I have a new battery coming today.

I have read the other thread on the DEM and I'm going to test the wires once I have the battery disconnected.

If no joy ill get the DEM sent off next week.

I've been looking at servicing the Haldex, changing the oil / filter whilst the DEM is gone but its the 3rd gen and look like an absolute nightmare :confused_smile:

Consider :

As you are going to loose the haldex oil when you remove the DEM unit, why not remove the oil 1st. If the oil is relatively clean, you can assume the filter will be no dirtier, and may consider just replacing the oil when you replace the DEM. If the oil is minging ( and you'll know if it is - I've read reports of clean oil to almost a semi sludge removed. Mine was very bad, but I blew air through my removal tube to disturb floor lying sediment and get it out of the haldex) then you may need to revisit the question of filter replacement.
The nightmare is not the removal of the dem or filter bolts as IIRC it can be done without removing exhaust/prop, but what happens if you SNAP one of the dem/filter bolts - that the NIGHTMARE !!!! esp the filter ones.
Use a good quality 1/4" socket set, and consider cutting down the hex keys that fit the bolts to give more access. - Thats how I got access to my filter ( haldex 2) , but the filter bolts did not what to come and I did not want to risk snapping them. Steel bolts into aluminium castings never easy to remove.

Cheers
Bob

Cheers
Bob

That's a good idea, so did you use some sort of pump to suck out the old oil through the drain or DEM hole? I was thinking about doing this but I was concerned about breaking something. But I guess it will be a lot easier than dropping the prop shaft.