Electrical/Computer Fault - Anti Skid/Brakes

[rhorne]

I've read many a post on here from people with similar issues to mine but I'm so far drawing a blank so thought I'd post my particular symptoms in the hope that someone has had the exact same problem.

I have a 2009 Volvo V50 2.0 Diesel Type R Design.

Lately I've started receiving the dreaded "Anti-Skid Service Required", which by itself is nothing to worry about, but this is usually almost immediately followed up by the quite scary "Brake Failure - Stop Immediately" and my car limping to a halt.

If I pull over, turn off the engine, lock the car and unlock it again and wait a couple of minutes it usually fires up again as though nothing has happened and I can drive off on my merry way again.

This can happen once and then not again for weeks, or, as happened at the weekend can happen every ten or so minutes.

I have a friend who's a mechanic and has a diagnostics kit and he connected my car up but said the log was absolutely choc-full of faults about all manner of things: power steering, brake lights, turbo charger, reverse lights etc - all of which are working just fine. He reset the logs and told me to drive until the fault happened again. I did this but when he ran the diagnostics check again, the log was full of random faults again. My pads and disks are totally fine, by the way. I'm not sure about brake fluid - this might be worth checking.

I read on here that people have had similar issues and resolved it by replacing the sensor/switch on the brake pedal. We did this yesterday as it's only a cheap part, but yet again today I got the Anti-Skid service required message. Now interestingly, this wasn't followed up by the Brake Failure message and I was able to drive normally with the orange warning still on my dash.

Again, after parking up and setting off again after lunch, the error had cleared and everything was fine. It's too soon to say whether this repair has had any effect and I might just have got lucky today, but I will keep an eye on this.

To give you some additional background, In the last 9 months I have had to replace both the battery and alternator, though they are both testing as fine. In the last 2 months I have also replaced all four tyres, though this has not coincided with the aforementioned fault.

I also was, for a while, receiving the "Engine Service Required" warning light with my car's speed limited to 30/40 mph. This usually happened when I was accelerating up a particular hill. I'm not particularly mechanically minded but it almost feels like the turbo splutters briefly in third gear and this caused the warning. Again this would go away after restarting the car. This seemed to go away completely and hasn't happened for a while but could explain why there are issues relating to the turbo charger in the log. My mechanic says veins on the turbo charger can sometimes get blocked and trigger this warning. I have no idea if this is true or not.

I also have an issue sometimes where when I start the car up, I have to hold the ignition for 20/30 seconds before it eventually splutters into life. After that it's fine again. Apparently this is an intermittent problem with the fuel pump and could be a small air lock.

The Engine Service and fuel pump issues are less important and I'm not asking for advice on those just yet, but thought they were worth mentioning as they might be contributing to the logs. I'm trying to give out as much information as possible in order to help diagnose the issue.

Thanks in advance.

[Sasha94]

ABS pump springs to mind if the diag unit isn't showing a faulty ABS sensor. Failing that if there are lots of faults appearing check all the fuses and connections on the CEM unit under the glovebox, it's liable to get kicked, if any are blown then change them and try again. My old S40 gave me the Anti Skid warning and brake failure message along with Engine System Service required and the EML blinked a few times in my ownership accompanied by the Power Steering system service message and the cause of the warnings was a blown fuse in the CEM. The other thing that happened was the Rev counter stuck on the reading it read when the Anti Skid light came on for a bit before dropping to 0 and the temp gauge goes over to read cold.

The root cause was never found but it didn't happen again in my ownership

[Bloders2]

what are the fault codes
some may be spurious. some may be useful/.

[rhorne]

Originally Posted by Bloders2

what are the fault codes
some may be spurious. some may be useful/.

I haven't got a record of the fault codes. When my mechanic connected it up whatever log he was looking at was just a huge long list and we didn't write any of them down.

[rhorne]

Originally Posted by Sasha94

ABS pump springs to mind if the diag unit isn't showing a faulty ABS sensor. Failing that if there are lots of faults appearing check all the fuses and connections on the CEM unit under the glovebox, it's liable to get kicked, if any are blown then change them and try again. My old S40 gave me the Anti Skid warning and brake failure message along with Engine System Service required and the EML blinked a few times in my ownership accompanied by the Power Steering system service message and the cause of the warnings was a blown fuse in the CEM. The other thing that happened was the Rev counter stuck on the reading it read when the Anti Skid light came on for a bit before dropping to 0 and the temp gauge goes over to read cold.

The root cause was never found but it didn't happen again in my ownership

That sounds like it might have some legs, actually, as power steering was another of the faults that showed up in the log.

[Sasha94]

I don't remember which fuse it was off the top of my head but test them all and if you find a blown one change it and see! Might be lucky

[Bigchewie]

it does sound like some dodgy leccy there, like was mentioned a dodgy fuse or possibly a bad earth strap/point?

[martin93]

Check the connections on the CEM in the passenger footwell. I've heard the big plugs can come loose and cause all manner of electrical gremlins just like the ones you are experiencing. It's the white thing with all the fuses.

Hope this helps!

[upv5]

Without the codes it's difficult to narrow down but another cause is metallic particles stuck to the ABS magnets in the wheel bearing, a good blow out with an air line resolves this and it's cheap/free. When it happened to SWMBO, her V50 threw several warning messages including headlights and steering but the code for RH front ABS wheel sensor was the real culprit.

Best of luck.

John

[RuanEllis]

Just an FYI - my car regularly has the same problem, I'd almost put money on it being the connectors on the CEM (white unit under passenger side of dashboard)... The pins in the plug seem to go loose over time and cause communication errors on the high speed CAN network, which is connected via these plugs.

The reason for this is that the ABS system and DSTC system reads information such as current engine torque, steering angle, throttle pedal position and the ABS/DSTC system requests engine torque intervention for DSTC/ABS via the network also. When a fault is registered on the network, the systems will immediately halt, since they are safety critical systems... Usually reseating the connectors will resolve the problem.

My car has been owned by my family for almost it's whole life - 10 years (it's MY05) and there's been probably close to thousands spent on this problem, with no resolution. New ABS pump, new engine loom, new throttle pedal etc...

Don't go spending thousands on replacing all manner of components before you've checked this!

As a side note, the sunroof drains and AC drains from memory if blocked can overflow and literally pour onto the CEM... The PCB inside is conformally coated, so it's unlikely to damage the actual PCB, however the connectors cannot be, therefore corrosion on them is entirely possible and likely!