ABS rings

[Namo Amituofo]

Dear all

I'm fairly new to this forum (and to mechanics) - had a disastrous day today thanks to my XC90's ABS warning - and found this thread on Google. I wonder - if my car's problems are caused by ABS ring? Please could you take a moment to read details below and give me your thoughts? Any tips would be much much appreciated!

For my very old 2004 XC90 T6 - I've recently replaced serpentine belt and tensioner/pulley - and for this job I removed ECM TCM modules as otherwise the tight clearance made the job literally impossible. I used a ECM/TCM removal tool and disconnected battery negative on a cold engine before the job. After the job, I reconnected battery and turned ignition to position II - did a test drive and all seemed OK.

Today I had the 3rd trip after the job mentioned above - and I was stuck in really bad traffic for 45 min - I pretty much didn't use the gas pedal as could just rely in pressing/releasing the brake to move at that slow speed. Then - suddenly - ignition was playing a bit funny - it was 'auto switching' off/on itself multiple times (sorry don't know the technical language for this) - at first I thought it was due to engine being idle for too long - but then the frequency increased to once every 30 seconds also - at which time 'airbag service urgent' warning message also showed up.

I continued to drive (in bad traffic) - and suddenly the 'brake failure stop safely' message came up - at which point I lost all electronics - gear light was gone, DIM was gone, and signal lights not working - but the engine was still running and I was able to accelerate / brake just like normal. However once cleared of the traffic jam I had to pull over (without being able to signal...!) to switch off and on ignition - which gave life back to all electronics - only to get the same 'brake failure stop safely' message again within a couple of minutes...

Luckly when the above happened I was close to home - still had to stop / switch off/on ignition 4 times to get home - and did all this with our little baby aboard!! I remained calm and get us back home safely eventually.

Some FACTS:
- Starter motor, starter switch and ignition barrel was changed in Feb 2017 (by previous owner)
- Brakes were serviced late last year (by a good local shop) - all working fine
- I've recently disconnected ECM/TCM and reconnected them - car did two trips afterwards - both fine
- The aforementioned problems started with ignition playing funny - then 'airbag' warning message - then 'brake failure' warning message - then loss of all electronics.

my SUSPICION:
- The car had been stuck in bad traffic before (albeit just for a few minutes - not as bad as today's) and was fine
- the only thing had changed was ECM/TCM disconnection/reconnection - could I have messed up something with my amateur job?
- ABS ring failure as described in this thread?

Any help / advice would be greatly appreciated.

Thank you in advance.
Namo Amituofo

[SwissXC90]

You may be suffering a DIM bad solder joint problem, and you can get your DIM fixed in London for a very good price, see here:

https://volvodiagnostic.com/shop/ind...duct&id_lang=1

[RoyMacDonald]

There are a number of electrical corrosion issues that it could be. I would advise taking it to Charlwood Volvo. http://charlwoodautomotive.com/

Peter Suchy is brilliant at diagnosing and fixing electronic faults and will probably save you money in the long run.

Roy

[Namo Amituofo]

Originally Posted by RoyMacDonald

There are a number of electrical corrosion issues that it could be. I would advise taking it to Charlwood Volvo. http://charlwoodautomotive.com/

Peter Suchy is brilliant at diagnosing and fixing electronic faults and will probably save you money in the long run.

Roy

Thank you! Very good to finally know of an independent Volvo guy!

Have found this post - think the problems are very similar to what I experienced - so first and foremost will try to clean contacts in ECM/TCM - also ordered VIDA to further diagnose.

[Namo Amituofo]

Here is an update - I just cleaned contacts in ECM/TCM (noticed the ECM purple plastic holding tabs have almost 'rounded' where the ECU removal tool inserts - so suspect it was removed multiple times before mytime).

Upon reconnection battery, turned key to position II - still had engine light, engine light, and ABS light on. Turned key to ignition - all these lights were out. I then drove around the neighbourhood (up to 30 mph) - no problems.

What I don't know is - if the problems would recur - if so I'm almost certain can rule out ECM/TCM connector issue - as these are in top condition - no corrosion whatsoever - yet I still gave them a good cleaning today.

So will drive on a bit to see if problems recur.

Will follow up as and when.

Many thanks all - I really appreciate it!

Namo Amituofo