ABS light ON ... MOT fail (of course)

[gloster_man]

Hi all -

My 23-yr old V70 had a few issues for the MOT and failed on several, most of which I've been able to fix, but the biggest and most persistent is this. My mechanic (in a backstreet workshop, but he knows his stuff) used his diagnostic kit through my OBDII socket to determine that the wheel most likely to be causing the fail is the OSF. In following the Haynes I have located the sensor in the steering knuckle and taken out the bolt - but it will not shift. Is all I can do: order a replacement while destroying the original, and hope that I haven't affected the seating ? And do I need to take the hub off too ?

Anyone's gained experience would be most useful, and much appreciated.

[amazondean]

I wouldn't rely on the OBD telling you the correct answer! It is quite possible that your ABS module is playing up. It is much easier to get out than a sensor, but replacing it with a good unit might be more problematic!

It will be cheaper to change the sensor and I'm sure a garage wouldn't charge too much to replace it for you, but don't expect it to sort the problem!

[cheshired5]

On P2 models, the ring on the driveshaft which the sensor reads is more often than not the cause and replacement solves the problem so carefully inspect everything. A sensor fault code does not necessarily mean a sensor fault.

The sensor should just pull up once unbolted so is probably held in by silt and years worth of debris.
Take your time.

[volvo again]

Can be a pain to remove, plenty of WD40 or Plusgas, once bolt is out try levering side to side to free it off, clean out hole before replacing new one, and as said, check reluctor ring, these can rust and split

[stevepcar]

I had a problem with my ABS which was intermittent. So after removing the sensor & cleaning it (it was filthy) I also managed with a small screwdriver to clean accumulated rust & other debris from the teeth of the wheel that the sensor reads. This cured it for several years, (Its called a Reluctor Ring) they are still available, there is a you tube video that explains how to replace it, if you are that handy. It involves heating the ring up in the oven & fitting it to the hub. But I expect a garage can fit it for you. Good luck

[Joe Harding]

I tried to fit a reluctor ring by heating it but it lost heat too quickly. CheshireD5's video uses a soft hammer and silicon grease to ease it on. I can confirm this works although it is one of those operations that can take two minute or an hour.

Satisfying to do though, especially as the Haynes manual describes it as a 'specialist job.'

[Bob Meadows]

I completed a bit of a write up on this to include all the problems being experienced:~ (a search should find it)

Wheel sensors (front) they tend to seize as previously mentioned- keep soaking with release fluid and tap the bolt holding arm gently from side to side to loosen the rust grip, once free clean all areas and coat with copper grease.

Reluctor rings :~ I used heat (oven) with light taps to replace- some companies do a liquid bonding but I've never used it- the hub will have to be dismantled in part but not difficult once the ctr Bolt or Nut is removed.
Front rings can rust & split so worth checking.

ABS Module:~ I would certainly take a look at this (plenty of forum details) don't butcher the cover- it can be done neatly and simply - soldering is quite straight forward as forum advice etc.
Check cable & plug making sure the lid cover locks/snaps into place properly-

I would look at the module first.

Good Luck
Bob