I've had my 06 S60 2.5T AWD for about a year and this winter the AWD has been sporatic to say the least.

When you start the car and take off, it works perfect, grips good and I can step on it and kick out the back end if I wanted to, for about 30-40 seconds after I start it. After that it stops, the rear wheels no longer engage and it's all front wheel spin. Pull over, shut the car off and start it again and voila, another 30-40 seconds of perfectly functioning awd and then once again it stops working.

No strange noises, no error codes, no lights, other than the traction control flickering when it starts spinning in fwd mode only. No leaking fluids, everything seems perfect other than it ceasing to have awd after about the same amount of time, all the time. Seems like cutting the key power resets things and it's back to normal.

I've read about the DEM/fuse and other issues. I haven't actually opened up the DEM to check it but it would seem to me if it was fried then it would just never work. So I've wondered about the pressure/temp sensor in the rear diff, maybe it does a check after so many seconds after start up and sees and issue so it disables everything.

Looks like this sensor can be changed on it's own? Worth a try maybe?

I'm no newbie to AWD cars or mechanics, I have a near 600awhp racecar as well as a Subaru but this is my first venture with the haldex awd system. Any insight would be very appreciated.