Xc90 fault, abs? Yaw sensor? Water in footwell? At a loss!

[Spd]

Hi,
Hoping someone may be able to help. I have a 55 plate xc90 which had abs light and warning appear. Following this, the car lost most of its power and warned me, ‘brake failure stop safely’. After restarting the car, warnings had disappeared but then came back with loss of Speedo, temp, fuel etc. Upon plugging in to diagnostics it was discovered a new yaw sensor was required. This has now been replaced but the fault was still there. It will now not communicate at all with snap on modis ultra or vida.
Wondering if it has anything to do with the water I’ve heard in the passenger footwell. All fuses have been checked as far as I know. Everything else seems to be working okay, aside from the seatbelt sensor/alarm not triggering.
Grateful for any input! 😊

[SwissXC90]

Water in the foot well is not good

You have to lift your carpets and insulation to dry them out
You have to find the source of the water leak - either sunroof drain or CEM cable entry from scuttle panel under windshield

If CEM has had water in it it will be likely water damaged and likely to be the cause of all or many of your issues

[Spd]

Hi,
Thank you for your input. The plan is to take up the seats and carpets tomorrow and dry everything out. Did wonder if the cem was affected by this so will definitely check that out! The water has been there for over two years. Would that affect the diagnostic communication ability?
Thanks 👍

[nu11eaf]

Originally Posted by Spd

Hi,
Thank you for your input. The plan is to take up the seats and carpets tomorrow and dry everything out. Did wonder if the cem was affected by this so will definitely check that out! The water has been there for over two years. Would that affect the diagnostic communication ability?
Thanks 👍

Has the car got a sunroof, water in the footwell is a classic sign of a blocked or cracked or parted sunroof drain pipe, if it has, remove the A post trim either side of windscreen and check the drain pipes. There are threads on this problem on here.

[SwissXC90]

Originally Posted by Spd

Hi,
Thank you for your input. The plan is to take up the seats and carpets tomorrow and dry everything out. Did wonder if the cem was affected by this so will definitely check that out! The water has been there for over two years. Would that affect the diagnostic communication ability?
Thanks 👍

Two years is a VERY long time.

If you have had water leaking into the vehicle over two years, and if it is happening through the wire loom entry through the scuttle panel to the CEM, then you can guarantee that the CEM has a lot of corrosion damage.
Letting it knowingly go on for two years means the chances of being able to repair the CEM will diminish hugely and leave you potentially with only one option: a new CEM (and likely cable loom repair and new pins on the cable loom - rather time intensive)

If the water leak is the sunroof drain then the chance of CEM corrosion is lower but damage to the yaw sensor and audio amplifier are likely to occur, due to where they sit in the car.

If the water leak is a door seal then likely no CEM damage but still likely damage to yaw sensor and amplifier.

Given that you saw you have diagnostics communication problems, you need to know that the CEM is the main "brain" and the CAN buses go via the CEM and if any CAN bus is not working, coupled with other strange seemingly unrelated problems then you may be suffering CEM failure.

Alternatively, you may have DIM (instrument cluster) failure which can be readily repaired but is normally due to failed components and failed soldering. Unlikely to be water damage in the DIM

Water leaks should always be fixed immediately they become known because the water will cause corrosion to start on metal parts, and mold and mildew to start on cloth / insulation parts.

[Spd]

Hello and thanks again for your replies.
Yes I do understand that two years is a very long time for water to have been left sitting in the footwell. It seems to disappear quite quickly and hadn’t caused problems until now so I had not even considered it to be a major issue. Hindsight is a wonderful thing 😕
I’m thinking you’re more than likely right and the cem is severely damaged in some way so will be checking this tomorrow. I have no sunroof so assume the water is coming in from behind the dash. Again, something else to investigate!
I will update on progress tomorrow. Fingers crossed my car will survive!

[volvo for ever]

windscreen bonding for water leak

if you get code read and let us know please,

perhaps yaw sensor was just 1 fault you may have other underlying faults in abs/ecm system
broken abs rings
abs pressure swithes x2
brake position sensor
so ideally get code read and we can go from there

cem water ingress if you remove wiper arms and scuttle and then remove square blue plug then see if its corrosion wit water

regards

[owenfackrell]

We had a water leak that turned out to be coming from the windscreen scuttle. There is a cover piece that sits over the fan inlet and ours had some how become dislodged and this was meant that any water dripping off the screen went straight through the fan housing and down into the passenger footwell.
I only managed to track it down by taking the carpet out and waiting for it to rain to see where it came in.

[Spd]

Quick update...
Taken out carpets etc in front to clear and dry out.
No corrosion to cem but have discovered that wiring to the yaw sensor can often be corroded when the yaw sensor is faulty through corrosion, so expecting delivery of this wiring loom later today. Fingers crossed that this solves the problem! Will update again when it’s done 😊
Thank you all for your input.

[binty]

Some great advice here about the leaks.
On mine it was coming from the bulkhead between the panels due to the cavity wax drying out.
It was a pig to find, but easy to cure.

I would recommend leaving the carpets out until you are sure where the leak is from.
(I made up a false floor using expanded foam so I could drive it safely).

The leak did not appear until had been soaked with a hose for about 40 minutes

Good news is mine has been completely dry over this winter so I am sure it is now fixed.

https://www.volvoforums.org.uk/showthread.php?t=271764

Good luck and please post some pictures of the yaw sensor repair.