I just recently picked up this car last year, the AWD wasn't working at all..brought it to the dealer and they replaced the diff pump..it started working but engages "REALLY" hard and after about 10-15 rev's of front wheel spin the rear wheels will finally engage. Is this normal, because to me it sounds like my rear diff is going to fall right out..makes this banging noise heard from inside, it just seems like the rear wheels engage after a much too long of a delay of front wheel spin.

I also own a LR2, so I'm not new to the Haldex rear diff, iunderstand how it works/operates.. just on my LR2 Haldex things are seemless unlike this S40 AWD Haldex..

..any ideas or is this normal??

 

My AWD would engage but it would take over 0.5s (i.e., many revolutions of the front wheels) and does so quite harshly. No noise though. I wonder if the noise you heard was just worn bushing bottoming out from the sudden load put through the rear differential from the Haldex unit engaging so abruptly.

The dealer is going to check out the system and get back to me on Friday, Dec 30. I'll post back here what I find out. In the mean time I think that the AWD lag is pump, solenoid or check valve related based on my very limited knowledge of this system (Hey, I only started researching this a few hours ago). Clearly the clutch pack in the Haldex is fine. The control logic, wheel sensors, etc. are probably fine too (at least in my case as there are no check-engine light or codes). That leaves the pump, and other hardware that actuates the clutch as suspects.

Mike

 

The dealer did an inspection and test drive and gave the AWD (and rest of the car) a clean bill of health. There was a code present for the AWD system about the pump not performing properly, but this was a one-time event that happened 15 drive cycles ago. The AWD system needed to be flash-upgraded first before the dealer was going to put any weight into the code. I have to agree. Random codes are a fact of life with modern cars.

I guess for now I'll live with the abrupt AWD engagement. Perhaps a computer upgrade will change the system's behaviour for the better.

Mike

 

I plugged in my new sino-DICE device and pulled a code: "DEM-P188974 Pressure pump performance. Mechanical failure. Actuator slipping".

I took off the DEM unit to inspect and changed the filter and fluid. The pressure sensor on the DEM looked pretty clean. No chunks or debris like in some pictures I've seen, just a little grey silt on the sensor's tip which I blasted off with some spray lubricant. I pumped out the old fluid -- about 500mL worth -- and topped up with fresh AOC fluid from Volvo. I ran the pump on a 12V source and it sounds like it's in perfect condition. I re-topped up the fluid after running the pump. Total fluid put in was around 600mL. Here's a pic of the old fluid:


A test drive later that day showed that the AWD was still not kicking in soon enough. A second test on a snowy road seemed a little better but more testing is required before I can say anything improved.

Mike

 

I did some data logging today of the activation of the all-wheel drive. Mechanically, everything seems to be working! I am starting to believe that my issues are software related! Perhaps this is why there is supposedly a software upgrade for the AOC system.

After several acceleration runs in an icy parking lot, I graphed what I think are the most relevant parameters:
- DEM-Requested Propulsion...: How much gas pedal you're giving
- DEM-Requested rear axle...: Always reads zero. A calculated value that is apparently not being calculated for some reason. Not a concern.
- DEM-Rear axle torque: A calculated value that is (I'm guessing) roughly DEM oil (and hence clutch) pressure x engine output.
- DEM-Solenoid current: Proportional to how open the "tap" is to allow high pressure oil to squeeze the clutches together and engage the AWD.
- DEM-Oil pressure: Proportional to how hard the clutches are engaged. I don't think it measures oil pressure pre-solenoid otherwise it would spike when the pump was forced on or when a front-rear speed differential is present (like at launch when the front wheels slip). Can somebody confirm this?

In the attached graphic, I performed four quick acceleration runs. The entire length of the test was around 15 seconds. The first small run and second longer run on the left side of the screen show the oil pressure (red) and requested propulsion (green) tracking together. This is good; the DEM is apply pressure to the clutch in proportion to how much throttle is being given. The solenoid current (black) is frantically adjusting to maintain the right oil pressure. This is also good. The solenoid current stays high even after I let off the throttle (just to the left of the centre of the image) in anticipation (I'm guessing) of reapplication of power. Then everything goes to crap.

Just to the right of centre you can see where I press down on the gas again (green line step increase); however the DEM solenoid and oil pressure don't join in for over a second. Why the delay?!?! Shouldn't the solenoid react virtually instantaneously? To me this looks like a software flaw, as if the computer refuses to engage the AWD unless some threshold wheelspin is detected. When the AWD finally does engage -- with a harsh thud I might add -- it stays engaged but only if I don't let off the gas for more than a fraction of a second (See how it's still engaged for the last run toward the right of the screen? I didn't let off the gas for as long a time as I did for the third run).

Bottom Line: The solenoid works, the pressure sensor works, the pump probably works, the DEM works, but the AWD doesn't engage soon enough! (insert obligatory emoticon here: ). Does anybody have any clue how to fix this? The dealer won't/can't tell me what's in the AWD (or was it transmission?) software update. It would cost >$100 to upgrade the software with no guarantee that it would do anything.



Mike

 

I hate just asking questions instead of helping but it's all I have.

The dealer is charging for a software update? Wonder if you could negotiate something like an oil change and he throws in the update. Or check if this is a recall item. He might be forced to update for free.

What is a sino-DICE device?

 

Ask away. We're all learning, especially me since I've only been a Volvo owner for two weeks so far.

I actually went to the Volvo Tech Info site and purchased the bulletins on the software upgrades (and a few others). It appears that the upgrades don't address my issues or are for later(!) model year S80 (and other models).

After looking over the schematic for the DEM () I'm thinking that my issue is caused by a faulty feed pump. If the pump were working properly the pressure sensor would read 1MPa (145psi) when the pump is activated. It doesn't; it only reads 0.15MPa. I'm sure the pressure/temperature sensor is working fine so the number is right.

"Sino-VIDA" is my nickname for my VIDA unit that I got mail-order from China, "sino" being the prefix used to denote something Chinese, for example, as in "Sino-American relations."

Mike

 

Ahhh, very well versed in all things China as I sit in Shanghai typing this......

Do you have a link to the unit?

 

I got mine from AliExpress.com. The vendor's name is OEMScan...
Wholesale 2012 newest car scanner tool volvo vida dice
$175US with free 5 day shipping.

I never bought from AliExpress before but I now highly recommend it. It was cheaper than eBay/Paypal. Payment is not released to the supplier until you are satisfied with the product. Nice.

Shanghai? Cool. Your profile says that you're an A320 captain?! [insert jealous emoticon here].

Mike

 

No need to be jealous. Being I am too old to start over I had to look for work overseas. China just happens to pay the best right now. Flying there is non too easy either. If you have a good job at home then count your blessings.

The funny thing is I was just in Shenzhen the other day. I wonder if they still make it? The link you posted shows the product no longer available. Going to need more searching on my part. Thanks for the info.

 

I just bought the thing a couple of weeks ago and the link worked when I posted it but now it doesn't. Shenzhen OEMScan Technology Co., Ltd., Store No.11188 still sells them. I just checked. Go to Aliexpress.com and search their store.

Mike

 

Thank you for the info. I would love to stroll in there one day when I'm staying over in Shenzhen and buy one. Since everything in China is negotiable, I wonder how much they want in rmb? Could be fun.

 

Hi Mike, and others.

I am currently trying sort out a similar problem... 05 T5, 6 speed. Worked flawlessly last winter. A few times this summer I thought "that was more slip then it should have been" but didn't pay much attention. My wife said she heard it "thunk" a few times pulling away from an uphill stoplight in the wet.

When the snow hit, we knew we had a problem. A few trips to the local independent Volvo specialist has resulting in the "replace the whole diff and haldex with a used one" prognosis, which I will not accept.

Without the fancy scanner I have similar results. Seems to work well when I first start the car, and pulling out of a snow bank on the side of the road it functions. I let of the pedal and go to accelerate again and I have a front wheel drive (with >200 Ft lbs and an open diff... fun) out on the street, when I lose it, switching the car off and back on restarts it, until I let off the pedal... Occasionally this doesn't work, but usually it does.

My plan is to pull the pump, test clean the filter and sensor, refill and see if I get an improvement. But I think I'm up against more then simple mechanics.

Perhaps the due date is up on these things... and we'll see more and more more problems

MAtt

 

Bump.

Any update?

 

I bought a replacement pump for my S80 V8. Haven't installed it yet. In your case it could be the pressure sensor in the Haldex unit, or (hopefully not) a busted power transfer unit (a.k.a. angle gear). I remember reading about someone with a XC90 that as complaining of intermittent AWD. He ended up replacing the angle gear (possibly even modifying it by welding the spline gear or something).

Mike

 

One year later and after a couple of attempts, the AWD in the V8 S80 is working! Just to recapitulate, I bought the car (2007 S80 V8) last year for a great price. The dealer gave the AWD system a clean bill of health, and gave me a nice bill for their time. The symptom that I was experiencing was the AWD kicking in harshly and only after lots of front wheel spin.

In the end it was not the AOC pump, but rather the pressure/temperature sensor that was the problem. This is despite the fact that the sensor seemed to work fine; I could read temperatures and pressures using VIDA and the data seemed credible.

The AWD drive is fully functional now, engages quickly and is highly effective--not quite as grippy as the Torsen setup on my departed Audi A6, but still great.

Thanks to all that contributed to this wild goose chase!

Mike