DEM 0006 and AWD recovery

[cantabrian]

I just got a VIDA up and running, and the main code I see on my 2004 xc70 (174k miles; bought it this summer) is a DEM 0006 - faulty pump signal. This verifies the sense I had that my AWD wasn't working, which came mainly from having my tires chirp from a stop. But drives fine otherwise.

So, I've been reading around, and it seems like removing the AOC pump and filter is pretty straightforward, though a little time consuming (taking out the driveshaft, dropping the exhaust, getting the flange off).

But my question is mainly this: if I go through this hassle, how sure can I be that the pump is the problem? So far, I've done two things, only to deepen confusion: 1) I just got a mechanics stethoscope out and listened to the pump. It sounds like it's humming. 2) I looked at VIDA stats, and it looks like the pump is doing something (attached).

So, to make my questions clear, I'm wondering:
1. If the pump is doing something (according to VIDA and the hum), does that mean it's working, or could it be working, but just poorly (and need replacing)? I've read about testing it with a 12volt battery. Should I try that? How exactly do you do that?
2. If it's failing, could it be repaired by taking it out, cleaning it out, changing the AOC oil? (Thus saving me the cost of a new pump)
3. And, above all: could this be the DEM rather than the pump alone? If it looks like the pump, should I be doing something now to save the DEM? I've read somewhere that a bad pump can kill the DEM, and I'd like for that not to happen.

Any guidance would be much appreciated. What steps should I take to get this AWD system up and running? If I should just go ahead and order a pump, and get to replacing it, great. But if I should consider other things, do let me know.

Thanks!

[vtl]

Did you check your oil level first?

Otherwise, yes, Haldex pump lives for about 10 years and then just die.

[cantabrian]

Thanks for responding! Well, I bought AOC oil last week and had planned on pumping the old out and pumping new in. But then I got this code, and I figured I'd wait on that, so as not to waste the oil. Thanks for showing me the idiocy of that move. If you think changing the oil now could be something to try, or rule out, I'll do it. It makes sense that low oil would mess with a pump's signals; would old oil do the same?

Also: by "check your oil level," do you mean just fill it? Or is there another way to check?

What do you make of the VIDA stats I attached?

[vtl]

Pump does not have a feedback loop, it is DEM who guesses if the pump has failed (because it applied X amps and got Y PSI on a pressure sensor, while Z PSI were expected).

When I got DEM-0006 (http://www.volvoxc.com/forums/showthrea ... D-concerns) and started replacing the pump, I found some suspicious "wetness". Dumb me didn't check oil level before committing into pump replacement, which cost me around $400 in parts.