XC90 ABS Fault

[gasc2188]

My XC90 has suddenly developed a problem with its brakes. When I switch the engine on I get the message "Brake Fault stop safely". If I try and drive the car the speedo fails to operate. Also when I switch the car on, I get lots of clicking from around the centre console / dashboard area. This clicking lasts for about 5 to 10 seconds.

I had the car plugged into the diagnostic computer which is a Lauch X431. It bought back 2 fault codes.

1..... ABS 0094 Cominication between control modules. Communication problem with active on demand coupling

2..... ABS 0100 Communication between control modules. Communication problems with the engine control module (ECM)

I checked all the wheel sensors for the ABS and they looked OK and the wiring to them was intact. I thought the best way forward was to send the brake control module off for testing. I disconnected the module from the ABS pump and sent it off for testing.

The module has been tested and showing no faults.

Has anybody got any ideas about what to test for next. I was thinking of testing the sensors, but I've got my doubts as the diagnostics havn't indicated any faults there.

Thank you in anticipation of any help.

[stuarthartley]

would maybe check relays next, i had same kind of thing on volvo wagon and it turned out to be 2 pound relay

[gasc2188]

BBA were really good. They tested the BCM and said as far as they could see it did not have a fault, and they did not charge me either for the testing or the post and packing to get it back to me, so it cost me the £6.20 for registered post to send it to them. I made sure all the pins on the multiplug which attached to BCM were clean and plugged it back in. I also put a slight smear of petroleum jelly (Vaseline) on some of the electrical pins. Ive checked all the fuses and they are all fine. Couldn’t find where the ABS relays were located so would appreciate if anybody could tell me. I’ve checked the fuse box under the bonnet, in the driver footwell and in the boot, but there doesn’t seem to be any labelled for the ABS. Anyway sorry for rambling.

I re-connected the battery and crossed my fingers. It started and the red triangle did NOT come on with its accompanying message of “brake fault stop safely”, so I was pleased about that. Thinking maybe a dirty contact, however, the “Anti Skid Service Required” message came up and the yellow triangle. I also got the Transmission service required message. I drove it around the block and it drove great, absolutely no problem at all. I parked it up overnight and went to it today and started it up. Again no “brake fault stop safely” message, but still had the “anti skid service required” and “transmission service required” messages . Drove away no problem and got to a give way approximately 1 minute into my journey. The car then went into some kind of limp mode. It wanted to start off in drive 3 or a similar gear to that, and there were 2 dashes where the gearbox mode is normally displayed (i.e Drive, neutral, reverse, park etc). I pulled into a layby, turned the car off and then back on again and saw dashes were still there. Turned it off again, took keys out of the ignition and pressed the fob to lock the car. I then pressed it to unlock it, started up and everything was normal again although “anti skid service required” message had gone and just the “transmission service required” message remained. The car drove no problem at all. Within 15 minutes I arrived at my destination, stayed there for about an hour and a half and came out and started the car. To my amazement no messages and completed my journey home with no messages or strangle happenings. Car is now parked on my drive and wont be going anywhere until tomorrow.

I am wondering if the stored fault codes from before I took off the BCM and sent it off for testing have triggered the car to do the strange things. I am kind of keeping me fingers crossed but does anybody know anything which may help me.

I will update this thread if it is cured

[gasc2188]

Just thought I would put an update of my progress with getting my XC90 "perfect". I now believe my XC90 had 2 problems. The first was the ABS fault. BBA checked the module (BCM) and couldnt detect any faults in the unit. As mentioned above I put the BCM back on the car and although the Ani Skid Requires service message was still there, the Brake Fault Stop Safely had gone. I've today plugged the car into a Launch X431 diagnostic computer and deleted the error codes and the message has now gone.

With regards the limp mode, I changed the ATF fluid in the auto box. I opted for Amsoil which lots of people recommended, but NOT cheap, but the best rarely is. The gear change is now almost un-noticeable. The old AFT was quite brown instead of the red colour it should have been. I thought that would have cured the problem with the car doing funny stuff with the gearbox. But this morning it did the limp mode thing again with the dashes and starting off in drive 3 until I switched the car off. This afternoon when the car was plugged into the diagnostic computer, I reset the oil change counter on the car. I erased all the codes and went for a 4 mile drive, at this point no messages, no triangles.

On my return I plugged the car back into the diagnostic, and no fault codes stored. Fingers crossed its sorted, but its a trip to Volvo if it isnt.

My thoughts at this time, the ABS message after re-fitting the BCM, was an historic code that was stored in the XC90's system before I removed the BCM to send it off, which triggered the message. And I'm thinking it was a dirty contact. The gearbox limp mode hopefully was due to the oil being over due for changing and the gearbox sensed this was the case and caused the error code to be created. And even after changing the gearbox ATF, the gearbox oil change counter had not been reset until today. Hopefully the car will now know its gearbox oil is clean and new and not create any more errors to throw the car into limp mode.

I will update if any more problems. Now going to fit the Dension 500 gateway to it which I bought on Monday :-)

[galloot633]

G
hope youve sussed it, but your symptoms are EXCACTLY the same as I had on my s80 , plus I lost reverse at one point ! it is well documented on the s80 forum but Ive not heard of it on the xc so it could be a coincidence , my faults were caused by a faulty abs module, which I repaired myself, again hope youre sorted, but just in case .....
dave

[gasc2188]

Hi,
Thanks for your post. I used my car on Saturday and no messages, no limp modes......brilliant. Havnt used the car until today because ive been at work and been using my girlfriends KA. Been out today......ignition on......damn bloody Anti Skid Service Service Required message on. Drove 2 miles and parked car up for 5 minutes. Got back in and started car and drove off. Within 30 seconds car in limp mode with dashes where the gearbox mode should be. Turned off the engine and then back on again and no problems. Drove to Loughborough (30 miles away) and went shopping. On returning to the car, switched engine on and again with 30 seconds car in limp mode. Turned car off and cleared problem. How did you repair the module? what year is your S80? I've heard that after 2001 the modules were much better but Im sure they must have a failure rate. I sent the brake control module to BBA for testing. They said it was communicating as they said it should, and were 98% sure it was ok. But because they couldnt be 100% sure it was ok they didnt charge me. Wondering what to do next. I may have a go at repairing the BCM if its that. Otherwise I may give up and send it to the local Volvo garage, but this goes against my principles and will make my wallet feel a bit vulnerable

[400-ascona]

Is it a D5 or T6? What year?

[galloot633]

Originally Posted by gasc2188

Hi,
Thanks for your post. I used my car on Saturday and no messages, no limp modes......brilliant. Havnt used the car until today because ive been at work and been using my girlfriends KA. Been out today......ignition on......damn bloody Anti Skid Service Service Required message on. Drove 2 miles and parked car up for 5 minutes. Got back in and started car and drove off. Within 30 seconds car in limp mode with dashes where the gearbox mode should be. Turned off the engine and then back on again and no problems. Drove to Loughborough (30 miles away) and went shopping. On returning to the car, switched engine on and again with 30 seconds car in limp mode. Turned car off and cleared problem. How did you repair the module? what year is your S80? I've heard that after 2001 the modules were much better but Im sure they must have a failure rate. I sent the brake control module to BBA for testing. They said it was communicating as they said it should, and were 98% sure it was ok. But because they couldnt be 100% sure it was ok they didnt charge me. Wondering what to do next. I may have a go at repairing the BCM if its that. Otherwise I may give up and send it to the local Volvo garage, but this goes against my principles and will make my wallet feel a bit vulnerable

my s80 was 1999 , sadly part exed her for my xc this summer, loved that car , theres an awful lot of info on the s80,s60,v70 fault ( and quite a bit of misinfo as well) so i went at the problem with an open mind, looking at my xc the module and mounting look similar, I've only seen the one faulty module (mine) but I reckon the fault is the same for all modules, some blamed faulty components or dry joints but none of it made sense to me ( i've worked on industrial electronics since theres been industrial electronics) the fault proved to be cracked soldered joints where the socket is for the multiplug, if you think about it the harness is hanging off the circuit board via those joints, Ive done step by step proceedure on the s80 forum, the one thing you do need is good eyes ! I couldnt see the cracks but my apprentice at the time spotted them straight away.
dave

[galloot633]

heres the article from the s80 forum,


" abs module repair
After putting up with my abs/stc failing repeatedly for the last two years I finally decided to bite the bullet and have a go at repairing myself. I started by trolling this site and the matthews volvo site for all the information I could find, theres loads of usefull hints which I will include, . All the threads refer to "dry joints" and modules going "bad", but for me dry joints manifest themselves soon after manufacture , not ten years later ! and I've never come across components that fail with the reliability that they seem to in our ABS modules !
So enough of the theory's heres a blow by blow of the repair.

remove the abs fuses ( my '99 model was 11 & 12 )

remove the airbox lid and filter

remove the airbox base, I found that by pushing a 9 mm socket with extension bar down on the two retainers front and back, the box was released, I then tied this out of the way on top of the engine, this was easier if you remove the hose from the ETM.

remove the two pin plug from the module by squeazing the two clips ,I removed the large multiplug after the unit was removed, using an E5 socket take out the four bolts, you now have the unit in your grubby little hands !

opening the unit, I got this from the matthews site and is brilliant ! remove the four star washers, then screw the unit down to a piece of plywood, I then got a piece of 3" flat bar and ground a chisel edge to it, then resting this on a block of wood I pried the lid off, it came off with barely a scratch !

now for the repair itself, for this you do need a good (young) pair of eyes, ( thanks Eddie) and straight away the breaks in the soldering on the board to multiplug are apparent, mystery solved , think about it ? one rigid, fragile circuit board with a great multiplug and cable hanging off it ! no surprise they fail. now just resolder all the socket pins.( if youre not too confident , you could take this to you local pc repair shop ) now run some silicon round the lid and refit it.

refitting is the reverse and, what joy when you turn the key and all the lights clear.

so, go on and sort yours
Dave "

[gasc2188]

Thanks Dave,
I've not had the XC90 long and this problem has almost become a personal vandetta to sort it out :-) The more I think about it, the more I think its the module. What threw a spanner in the works is BBA tested it and said it was OK but couldnt be 100% sure it was without faults. Which is like saying it could be OK, but on the other hand it could be faulty. Having said that, sometimes the car is fine and doesnt present the "Anti Skid Service Required" and doesnt go into the limp mode, so it could be that when BBA plugged it onto their testing rig, it was behaving itself. It does seem strange though that before taking the module off it had a red triangle on the dash and saying "Brake Fault Stop Safely". Having sent it off to BBA and then putting it back on the car the Brake Fault stop safely message has never come back. Im thinking that with manipulation at the multiplug by taking it off, its moved the pins fractionally on the PCB inside the module and created a different short circuit or whatever they are called. I've not done anything else to braking system so I cant think of any other explanation. Thinks it definitely worth a try and all its going to cost me is a tube of sealant so not much to lose. Thanks for your advice and help mate, I'll let you know how I get on.