ABS Woes and MOT due imminently!

[liammedler]

Hi all, I've had an ABS light on for a while which tends to turn itself off in very low temperatures (2deg or below) but as my MOT is looking I thought I'd better get it sorted.

First I tried soldering the joints but that just meant the light stayed on at all times so I bought an OBD2 reader and read the codes:

ABS-141, 142, 214, 311, 312, 313, 314, 322, 323, 324

Quite a bunch, so I figured my soldering job wasn't up to scratch and tried again today. This time the codes are reduced to:

ABS-311 Left front wheel sensor
ABS-314 Right rear wheel sensor

Does this sound like my re-soldering on the power prongs of the ECU are ok and I have a hardware fault at the front left and rear right sensors or is it more likely I need to open up the unit again and get soldering (again!)?

Any of the ECU re-soldering services online say that they only accept a "virgin" unit and I can't seem to buy another unit online anywhere.

My 1996 850 T5 is my daily for work so I really can't afford it to fail the MOT - any help would be much appreciated!

[nickm]

What is your soldering technique?

I know this is an early unit but the board may have a silicone coating.

My advice is get a brass wire brush (like a tooth brush) and give the board a good scrub on the pins.
Get some de-solder braid or a tool and work each pin remove the old solder and re flow with lead based solder.

and contact cleaner on the connector (not wd40)

[El Padrino]

Hi liammedler, sorry to hear you've the dreaded ABS light on nightmare. I've had it too.

Seems unlikely that both sensors are faulty at the same time. They may just need a clean and reseating. If that doesn't solve it, it could be the joints may need re-soldering on the module. I've not had to resort to this myself yet, but I can feel it coming soon.

A couple of useful threads from fellow members who had the issue too, might be useful for you:

https://www.volvoforums.org.uk/showthread.php?t=335591
https://www.volvoforums.org.uk/showthread.php?t=336043

[liammedler]

OK I've had the module apart again and resoldered all of the joints again, to no avail.

The ABS light refuses to go out, even after resetting DTCs using my OBD2 reader and going for a short drive around the block.

Do we think it could actually be the sensors? I would have thought clearing the DTCs would have got rid of the light until the car gets back up to 12mph and reads again but in this case the light never goes out.

Any ideas?

[nickm]

Originally Posted by liammedler

OK I've had the module apart again and resoldered all of the joints again, to no avail.

The ABS light refuses to go out, even after resetting DTCs using my OBD2 reader and going for a short drive around the block.

Do we think it could actually be the sensors? I would have thought clearing the DTCs would have got rid of the light until the car gets back up to 12mph and reads again but in this case the light never goes out.

Any ideas?

Check the wires to the sensors. Or swap the sensor reading as good to the bad hub

[liammedler]

Sorted!

Another check of the pins on the ABS ECU, some more cleaning/solder and an ABS sensor plug that wasn't quite clicked home has sorted it. Such a relief!

Now for the MOT ...

[cyclogenesis]

Have you checked the reluctor rings. I had issues with mine as they were corroded and the system could not read the speed of the wheels correctly. New rings and problem solved.