AWD not working. Need help troubleshooting.

**men2be** · 07-05-2013, 05:24 AM

2004 xc70 124k Recently acquired. I had parked in the wet grass. I purposely accelerated hard as a test to see how the awd system worked. Well, it did not. Front tires spun and left the proof in the grass, but the rears did not. Front end began to slide down the incline I was on. I did try searching but did not find any basic steps to take to start the process of troubleshooting.
Thanks in advance for your help on this. Car runs fine, no noises from rear.

**Xheart** · 07-05-2013, 06:51 AM

I take extra precaution when working on our cars.

I would raise it on four jack-stand so wheels clear the floor.

Set the shift to Neutral, and rotate the front wheel by hand, watch the propeller shaft rotate with it. For better visibility, place small pieces of painter's tape over the length of prop shaft, i.e. portions front and rear of the center bearing. Repeat with shift in Drive.

Shift in Park would set the two front wheels rotate in opposite direction.

Do not rush and be careful.

**JRL** · 07-05-2013, 07:13 AM

Start with the above.
Then run the car in gear on jackstands (slightly over idle is fine, 1500-1800 RPM)
Don't worry about the tape or shaft
If the rear wheels are turning, even the slightest, that means look to your DEM module or pressure sensor.
If the rear wheels do not move you probably have a broken collar gear or angle gear

**RockitShip** · 07-05-2013, 12:35 PM

Originally Posted by JRL

Start with the above.
Then run the car in gear on jackstands (slightly over idle is fine, 1500-1800 RPM)
Don't worry about the tape or shaft
If the rear wheels are turning, even the slightest, that means look to your DEM module or pressure sensor.
If the rear wheels do not move you probably have a broken collar gear or angle gear

I would like to add with the caveat that it is possible the rear drive shaft spins but the rear tires can be immobile, then there is something wrong with the haldex, such as the DEM.
No rear drive shaft spin usually = bad angle gear sleeve.

**JRL** · 07-05-2013, 12:45 PM

That's what I said

**RockitShip** · 07-05-2013, 12:57 PM

Maybe I'm splitting hairs in trying to narrow down the problem.
It is possible that the drive shaft could be spinning (without rear wheel movement) isolating the problem to the Haldex system not the angle gear.

**JRL** · 07-05-2013, 02:30 PM

Again, that's what I said.
The DEM module (and pressure sensor) are part of the Haldex system, it's pretty rare for the actual Haldex unit to have issues.

**Xheart** · 07-05-2013, 04:24 PM

A Haldex accumulating 100k over short trips will show relative wear, common maintenance item.
In addition, OP acquired it recently, we don't know what abuse it had with the set of tires.

**men2be** · 07-05-2013, 07:09 PM

Thank you all for the great info! I'll check it out and report back.

**tapanitja** · 07-06-2013, 10:12 AM

Hi gents,
I woder if we can make any conclusion of the fact there is no DIM message? caused by DEM pressure/temperature sensor or comms error as I'm familiar with.
Could it be as simple as the Haldex fuse in the rear, blown by worn out pump? If the Haldex oil / filter has not been serviced 124k migth be enough for the pump.
br Tapsa