XC70 2005 electrical issue
 

Hi all, I am new to the forum and I am hoping someone here would be able to shed some light on a strange electrical issue I’m having a problem trying to get to the bottom of.

My 2005 xc70 has developed an electrical issue causing numerous problems, due to it being intermittent though it’s proving difficult to pinpoint.
I can be driving and it will appear saying ‘anti skid temporarily off’. This will seem to put the car/computers in some sort of strange state so the mirrors and window ( also possibly other things) won’t operate. When I turn the ignition off in this state and remove the key. Numerous dash lights will stay illuminated. The lcd displays will show ‘srs-airbag service urgent’ there will be a red warning triangle on dash along with airbag, brake failure, parking brake and oil red warning lights and also the abs amber light showing. The vehicle will also not lock. To get the lights to go off I have to reinsert the key and start the car, ( it will then sometimes remember if I had asked it to close the mirrors earlier and comply). When I now turn off and remove the key all lights normally go off as expected and car will lock.

Sometimes the fault will occur without even driving the car, I will simply unlock it and this will cause the dash lights to all illuminate without the key even inserted.

Any ideas, would be greatly appreciated.

Kind regards
Josh
2005 XC70 D5 AWD SE lux

How many miles on your '05? General state of repair, please?

Absolute RULE #1 for horror stories such as these is: Do you have a healthy, fully charged battery and, because electronic paths are involved, a known good charging system?

When was the last time you even checked your charging system while running? You would've been looking for >14 charging voltage just for peace of mind.
Regular checks with a basic VOM help form beneficial long term planning.
EX: Monthly "first thing in the morning" voltage checks can show you the downward trajectory of all batteries.
No judgement here, just askin'.

Also, weren't there water incursion problems with some ECUs around 2005?
I'm foggy on this one but I believe the CPU is central to the dash as well as the base of the windshield.

I do know that your era of car experienced cold / cracked solder joints in the ABS control unit of some vehicles. This malady created a cascade of lights and malfunctions.
However, the SRS light etc. wasn't part of the faulty ABS card scenarios I recall.

As a longshot...how are your brakes? When they get low...when the MASTER CYLINDER gets low....when worn pads cause the caliper to rock more than usual, you can get a slew of codes.

Don't overlook spider webs and rust on disused ABS pulse wheels or accumulated dirt on the sensors.

Check your juicer first.

Hi there Georgeandkira and thank you for your reply,
My Xc70 has 96000miles and I have always kept on top of repairs and strived to keep the car in the best state I can. I also was swayed towards the battery at first, so I disconnected this and completed a full recondition using my ctek battery charger. The car also had a brand new Bosch alternator installed earlier this year.

You are correct in thinking the CEM is located near the drainage area just below the windscreen. I have removed this piece to check for build up of debris causing water to leak into the CEM and this was fairly clean. There does not appear to be a correlation between wet weather and the lights starting. I am not ruling out a possible CEM problem but due to the significant price tag I am trying to determine 100% the problem before jumping at it as a stab in the dark. All pads appear to be of good thickness and discs only have minimal wear in my opinion.

I appreciate your suggestions

2005 was a big year for electrical changes on the XC70.

So you could have either the earlier electrical system or the later one.

So if you have the earlier electrical system the instrument cluster did suffer form bad / failing solder joints which throws up loads of random errors, if you have the earlier cluster I believe the dials did not have chrome surrounds on them, were as the later cluster did and was not subject to the same problems.

If you have the later electrical system then water/damp in the CEM was a problem, but to check you need to remove the plastic scuttle panel and then the lid of the box were all the wiring enters to check the top of the CEM for water ingress. If you look under the dash in the drivers foot well you can see the CEM the later one is black plastic with no relays just a fuse box.

https://i.imgur.com/mxUXUvus.jpg

I would also suggest you read the cods from all modules to see if error codes are stored as this may give you a clue as to were to start looking.

As you have error from multiple systems I would suggest you look at these 2 possibility's first as it going to be some thing central to the system that has the problem.

As Georgeandkira suggested a good charged battery and working charging system is a must I would also suggest having a voltmeter connected so that when it happens you can see if you are getting a sudden voltage change either up or down , I have a cheap digital voltmeter that just plugs in to the 12V socket on the dash , it just gives you a general idea if things change suddenly.

Hi there XC70Bob and thanks for your time to reply with some advice.

I am pretty sure I have the later electrical system as you describe. I will try to do some more elimination tests over the next few days. Due to the issue not seeming to have a correlation to poor weather I am swaying away from water ingress into the CEM however I am not totally ruling it out, and it may well not be water ingress and just an internal fault, if it even is the CEM all together.

That is a good idea with the multimeter to check voltage when the fault occurs and I will keep this in the car for when the fault arises. And I will also strive to inform all of the codes if any stored.

Thanks again XC70Bb and any other suggestions or thoughts by anyone on what could be causing this annoying intermittent fault are greatly appreciated.

Kind regards
Josh

So if you have had water ingress on to the top of the CEM it can cause the connectors that are on the top to corrode so even if its not wet when the fault occurs just going down an uneven road or over a bump can cause movement and then you loose a connection.

You really need to look at the top of the CEM to be sure as I suggested.

Have a watch of this https://www.youtube.com/watch?v=U8UozG9qLvM
Its USA based so the CEM is on the opposite side to yours but it will give you an over view and you can see the connectors on the top of the CEM that suffer when you have water ingress.

Electrical issues
 

I had this same issue with my 05 xc70 last year. Came out of store and out of nowhere I couldn't lock my doors. Couldn't roll windows down. Entire instrument cluster quit working. But it was driving normal etc. I was at a loss. Turns our there is a black box type thing under the driver's seat. I took entire seat out of the car. There was this one black ground wire that had worn over time and was showing wire on one side of it. That ground wire was touching some metal under seat and grounding out. One little wire did all this damage. I couldn't believe it. Put electrical tape around the open side. Problem quit. That simple. Couldn't believe it.