http://www.volvosnak.dk/phpbb3/viewtopic.php?f=4&t=6792&p=35825&hilit=awd#p35825

http://xcforums.com/topic/32-diagnostic-how-to-awd-failure-dem-diagnostics/


Originally posted on V70R, but I'll put it here because I think many will find it useful.

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)

7. Review Tech-Net Note (TNN) 40-02 and perform DEM and Central Electronic Module (CEM) software
upgrade if needed.

8. If the DEM will not accept software or there are repeated communication problems after the
download and all checks are good, replace and reload theDEM.