2006 XC70 Major electrical faults

[gelertd]

Given my experience when the CEM in my 2006 XC70 suddenly started doing weird electrical stuff (which included a parasitic battery drain via the radio) and Vida showed up multiple codes in all sorts of modules (including the DEM) I would start with the CEM first.

It should be fairly evident (it was on mine anyway) when you get the two multiplugs off under the scuttle that some of the terminals on the top of the CEM have 'green crusties' on. That's a sure sign of water ingress that will have found its way via gravity downwards and into the CEM. Even if no evidence of water ingress I'd take the CEM out and send it to volvodiagnostic to have it checked - at the very least if all's well with the CEM you can eliminate it.

Check both multiplugs on the wiring harness that comes off the top of the CEM for corrosion too - only one of mine was effected and fortunately it cleaned up OK (replacement pre-wired multiplugs are available from Volvo that can be spliced into the loom).

[onyourbikenate]

from the document you linked it actually recommended replacing the loom as well, although i'll see what state its all in first, the car isn't drivable at the moment anyway so i've got time.

(online shopping, tuning my ears to filter out the mrs whining )

i know my AWD doesnt work, i can happily wheelspin the front wheels, and always have had the anti skid service required, if i'm going to work on it i'd rather get this working as well, looking at the haldex unit it doesnt look like its ever been serviced.

[pierremcalpine]

Originally Posted by onyourbikenate

- to get the haldex pump off looks like i need to remove the propshaft, is this a driveway job i don't have access to a ramp.

Yep, best if you get all four wheels off the ground as high as you can with jackstands but still fine if you just jack up rear. Don't kill yourself like I did trying to pry the prop shaft out of the flange - there should be two empty holes in behind the flange. Just insert something narrow in there after you have removed the 6x allen bolts and tap the prop shaft out. Have fun and good luck! Keep us posted. This is an interesting thread!!!

[onyourbikenate]

Ok so today removed the CEM, hardest part was getting the wipers off! I gave the nuts some wd40 last night and this morning the wipers were solid on there, more wd40 coffee and brute force and they came off eventually

Then was the scuttle plate under the windscreen that was ok just plastic clips, almost lost one of the middle parts down the back of the shock mount but luckily managed to get it out so I can reuse the clips

Then the wiper assembly came off easy enough, then the cem cover, mine does have the updated type which is a bonus, took it off and removed the connectors, bone dry. Then went in the car unplugged all the other connectors and pulled the cem out.

It looks fine no sign of any water damage but I'll get it sent off to rule it out.

Annoyingly once all done I noticed my drivers window agar! Luckily I have wind deflectors so shouldn't get water in unless there is some horrific storm next week. Typical!

Wish me luck guys anyway will let you know once I get the cem back.

[onyourbikenate]

Originally Posted by pierremcalpine

Yep, best if you get all four wheels off the ground as high as you can with jackstands but still fine if you just jack up rear. Don't kill yourself like I did trying to pry the prop shaft out of the flange - there should be two empty holes in behind the flange. Just insert something narrow in there after you have removed the 6x allen bolts and tap the prop shaft out. Have fun and good luck! Keep us posted. This is an interesting thread!!!

Thanks for the advice, I only have 2 jack stands at the moment, so can only jack up the rear, but i read you need one front wheel off the ground to be able to rotate the propshaft to undo all the bolts, so i might invest in another pair of stands, i need to get an impact gun anyway as apparently that nut holding the flange on is not easy to get off by hand.

as i said above my CEM is boxed up and ready to go for diagnosis, i'm keeping my fingers crossed that it is the issue, although i'll do the DEM and pump anyway i'd like a running car in the meantime, i can't trust to drive it in its current state, not only could it randomly leave me stranded but i don't think driving without a speedo is responsible.

I've got a lot of trips i want to do, i need to get confidence back in the car, but i am happy for the experience of being able to get stuck in with it, if i can fix it will be very satisfying

[palwing]

Originally Posted by onyourbikenate

”but i am happy for the experience of being able to get stuck in with it, if i can fix it will be very satisfying”

Fascinating thread. Thanks and please keep us updated with progress. As you say, fixing these cars is very satisfying and ultimately worthwhile. There aren’t many “modern” cars you can tinker with anymore.

[gelertd]

Encouraging that you have no evidence of terminal corrosion - at least you won't have the complication of a potential loom repair.

Outwardly, other than minor terminal corrosion, the CEM in mine looked absolutely fine. However, despite its outward appearance the actual circuit board within was heavily corroded (I don't think the board has any form of protective coating on it).

It may sound strange but I actually hoped my CEM would be faulty as it would explain all the electrical issues I had. The repair to my CEM saved me over £1000 compared to a new CEM from Volvo that would have to be coded to the car.

I am grateful for the advice and experience of members on this forum who posted their issues with corroded CEM's on similar model year V70/XC70's that enabled me to diagnose my problem and point me towards volvodiagnostic for the repair.

I hope you have similar success with your CEM - and look forward to an update in due course.

[onyourbikenate]

Update on this, spoken to lucasz at volvodiagnostic. he can't find a fault with the cem so he suggested i send him my dem and he will test that as he thinks that is likely the fault.

so now just need to get it off the car and packaged up.

just praying those bolts don't snap when i try undo them...

[onyourbikenate]

Had a spare half hour or so this afternoon thought i'd see how easily this DEM would come off. well i couldn't get it off.

the bottom bolt was easy it will come out no issue, but the top one. No clearance to get any tools in there other than a standard alan key, and i just couldnt get it to budge with an allan key, in the end stopped for fear of rounding off the bolt. sprayed it with a bit of wd40 and left it for another day.

the plugs as well on the back are hard to get to and didnt want to budge, couldnt figure out the clips as i couldnt see them.

they don't half make it difficult.

[onyourbikenate]

Well had another crack at the DEM removal today, couldn't of gone worse to be honest.

i bought a new trolley jack, and its useless chinese garbage, barely lifted the car an inch! rubbish.

with that though i managed to crawl under the car, got the connections off the DEM without too much drama.

the bottom bolt on it is ready to come off, but the top one is rock solid, i bought some sockets with allan ends on them to allow me to get a bit more force on it than a normal allan key, and managed to just get the tool on the bolt.

but then it still wouldn't budge, and in my attempts it rounded off the bolt, so now there is no way to get it off really. can't get any tools in the gap, so couldnt drill it out without presumably removing the haldex unit from the car altogether.

think i need to cut my losses with this car. the engine is great, the body and interior are in great condition. but sadly its just one thing after another with its electrics and with 180k on the clock, i think i have to draw a line under how much i'm going to continue throwing at it as i imagine paying the £1000 odd i would need to get a garage to remove this DEM, get it repaired plus the pump replaced etc, then no doubt something else will go on it.

think i'll get the CEM back, put it back together and then look to sell it spares/repairs and get something else.