My understanding of the system is that the Prop shaft should/will ALWAYS be turned by the car, as it constantly turns the Haldex input shaft.
The Haldex is a mechanical/electronic clutch unit where the rear wheel transmission "joins" the front wheel drive, via the Haldex input and haldex output shafts. The Haldex is controlled by the DEM.

If the Dem "can" recognise that the Haldex input shaft is not turning, it might be able to interpret this as a fault. Below is a list of how to check the DEM unit:-

DEM diagnostics follow this order:
1. With vehicle up in the air, ensure the rear driveshaft is turning when in gear.
2. If the driveshaft is not turning, remove the angle gear and inspect the coupling sleeve between the angle gear and transmission. If the splines are not stripped, replace the angle gear.
3. Check for codes in the CEM for communication faults.
4. If the driveshaft is spinning, access the Differential Electronic Module (DEM). If there is no communication with the DEM, check for power on the Blue/Red wire, ground (Brown and Black wires) and network integrity by checking resistance between the Green and White wire. With the battery disconnected, there should be 60 ohms between the two wires.
5. Check the Active On Demand Coupling (AOC) oil pump for proper operation. After startup, the DEM will apply power and ground to the oil pump and you should be able to hear it run. You can manually apply power and ground to it. If it does not run, replace the oil pump. The oil pump can draw excessive current and blow the fuse for the DEM, causing the lack of communication.
6. Check DEM live data and monitor the AOC oil pressure sensor. Key on engine off reading should be 0.00 (+/-.08MPa). Start engine and recheck. With the oil pump running, pressure should rise to .38 (+/-.08 MPa)

Good luck

Cheers
Bob

Haldex whine XC60
 

Hi,
My experience was a whine/drone from the rear of the car at about 70mph, from new.
After nearly 3 years (!) and much too-ing and fro-ing with the dealer, this was traced to the Haldex unit by a Volvo engineer who eventually graced the garage with his presence and almost immediately identified the cause of the noise.
The Haldex unit is allegedly "sealed for life" and there is no mention of opening it in the Volvo service guidance at that time.
The engineer said "open the unit and clean it out". The garage found extremely fine millings in the oil which had collected in the filter. Assume because the unit had not been adequately rinsed during manufacture.
Cleaned out, new filter, reassembled - problem solved.
Given the speed with which the Volvo engineer traced the problem we can only assume that he had encountered the fault in other cars.
Volvo do not acknowledge that this is a repeated problem.

Strange that VW/Audi service the oil and filter every 20K and 40K in their haldex units, but then again they have better access to the components. On the Volvo VIDA requires that you remove the exhaust and prop shaft @ mega £ /hour labour to get access to a <£50 filter.
Call me a cynic, but I bet that's why its "sealed for life."
There's a similar "servicing arrangement" with their automatic transmission fluid too.

Cheers
Bob

"sealed for life" seldom means precisely that. In transmission terms it usually goes with a fluid that keeps within spec for an average of 100,000 miles and gradually goes further below spec from then on, until the gearbox or transaxle probably fails at between 150k and 180k. Oil changes starting at 80k and then every 50k or so might well extend the service life by another 50k to 100k miles.

It all depends on whether the car is expected to last much more than 150,000 miles or 15 years, which is about as much as most cars tend to last before being crushed.

As to the Haldex rear transmission specifically, I have zero experience of its service life or requirements but suspect that it will benefit in the same way as automatic transmissions as explained above, possibly at shorter intervals but that's only a guess.
I do have some experience with the Honda unit, which is very like earlier Haldex units in principle. Honda specify 80,000 mile change inervals I believe but mine started groaning at just over 50,000 miles, so I dumped the fluid and flushed it by changing one more time after maybe five miles, and the noise has gone. No filter on the Honda unit that I'm aware of.

Bob,
I have the same issue with no AWD,I can spin the propshaft freely so I have bought a new splined kit to replace what I hope is my problem,my question is how do I use Vida to check the live DEM data,I've got a working Vida Dice but not experienced enough with it yet to use it properly ? It doesn't throw any fault codes bar for a couple of non related issues,I'd like to try and find out if my Heldex unit is working correctly before I start the job of taking the angle gear off and replacing the spline,if my Heldex unit isn't working right I'd rather not start the job and leave the car in 2 wheel drive.Any help would be appreciated.

If you can spin your prop shaft when the car is in gear and the rear wheels are on the ground its 95% certain the collar sleeve in the bevel gear into which the drive shaft locates is stripped. I believe sometimes they are not an easy job to remove.
I too am no VIDA expert, being torn between wanting to experiment, but being terrified of screwing something major up.
I suggest as a start looking under Diagnostics/Vehicle Communication. Then selecting the DEM icon in the LH screen. Then Parameters, which will give you a list of options which you can select by clicking and then clicking the "add to list". This then shows real time data for the selected item in the RH screen. Check out Oil pressure + Solenoid current + Pump current + DEM voltage. These parameters should give you enough live data so that you can tell if the item selected is working. There will be differences for example between engine off (ignition at pos 2) and engine at idle or 2000rpm. It is possible to graph the results, so you can see data over a few seconds time period, but when I tried it just confused me.
At the Parameter tab there are additional tabs for Activations or Programmed Values and Advanced. I can't remember what they are about but think they follow the pattern set by the Parameter tab ie select the module icon in the upper LH screen area.
As you say you don't have a DEM specific DTC, Id be reasonably confident that your issue with the AWD was down to the stripped collar sleeve.
One last point I'd make is Haldex oil. Get a couple of litre bottles from Volvo and rotate the contents through the Haldex unit. You have to vacuum pump the contents out, but you'll get the hang. Each time before removing the Oil get a tube and insert it as deep as you can into the Haldex and blow air through the tube. This is to disturb as much crud in the haldex as possible, so that when you drain the oil this crud is taken with it. Store this oil in a glass jar and leave overnight. I had 1" deep crud in a 4" jar for 6 oil changes before I saw any improvement. I recycled the top 3" of oil - I knew it was going to be removed.
I also removed the DEM controller and cleaned the pressure switch and the Solenoid, using a 9v battery to activate it. I think I used petrol to soak the two units, but not 100% sure.- both were full of crud.
Sorry if this has been a bit long winded, but wish you success.

Good luck
Cheers
Bob.

Thanks Bob,the more long winded the better as far as I'm concerned,I will do what you suggest:thumbs_up:

AWD trouble
 

Seems like I have the opposite trouble.
My 2005 S60 2.5 awd seems to have the rear diff always engaged. I first noticed it when attempting a tight u-turn. One rear tire skidded along like a 4wd truck that was bound up on dry pavement. We put it up on the lift and with the transmission in neutral we turned both rear wheels in the same direction. This resulted in the driveshaft turning. This shouldn't happen because the haldex only engages when needed and the car was off.

A little back story on the car. It has 74000 miles and appears to have been very well maintained. I bought it from a Copart auction and it needed a front bumper, crash bar, and one headlight. No hood or fender damage but the right frame rail neede a little pull. I don't think the awd issue has anything to do with the collision damage.

I have posted several threads/posts on Haldex issues and your issue is VERY similar to my issue.
My awd made a sharp bang/cracking when I tried to do a 3 point turn and I described a feeling of " locking up" thread is in this section.
Short answer : was a DEM failure which Lucus fixed for me. About 4 yr ago. Been 100% fine since then. I did have a Dem0005 vida code.
Search "sounds expensive" in pre 2007 v70 (P2) section.
Can't put link up as not at computer - using phone n can't get it to work lol.
Cheers
Bob

Hi. Iam a newbie ish so please understand .Iam hoping I am in the right area.
I have a XC60 2012 manual box with AWD. 100k on clock. New to me!
It has a gen 5 unit.Just changed the oil and cleaned it out.
My simple question. If I park on a muddy surface, set off the front wheels slip for split second then the back wheels turn and I get a grip and travel on the slippy mud ok.
So I guess at this moment all 4 wheels are powered.
Am I correct to say my AWD system is ok?
Regards