ABS Light stays on - How do I see which sensor has failed ?

[John-M 0]

As the title suggests - my ABS light is now staying on, suggesting one of the wheel sensors has packed up.

 

At switch-on, the light flickers for a couple of seconds, as per usual - but doesnt go out as it used to, at about the same time as you get the wee 'clunk' that you can feel on the brake pedal, which still happens.

 

A local VW specialist hooked up his VagCom, but it seems it wasnt able to 'talk to' the ABS controller to get the info. Maybe something to do with my 24V conversion ? Or maybe a diff fault :(

 

Is there any other easy way to determine which of the wheel sensors is not responding ?

 

Any help greatly appreciated.

 

BTW, I suspect that it is one of the front sensors that has failed. The light stayed on a few weeks ago but after I disconnected and re-connected the two connections in the engine bay it seemed ok. Stupidly I didnt do the 'try one side at a time' technique, so I dont know which side was the culprit. Doh !! I have disconnected/reconnected all 4 connectors now, to no effect.

[nocrap 0]

VagCom should show you exactly which sensor has failed especially on a VR.

 

Perhaps he'd set the baud rate for a different car and hasn't changed it back, that would make it fail comms

[Guest]

Can't help with finding out for sure but history shows that it is usually the front, nearside.

Thats the one that picks up most muck from the gutter in all the miles travelled.

 

If it is a case of fit a new one and see what happens I'd start there... unless you know of recent issues with another corner that could have caused damage to one.

[John-M 0]

OK, thanks for that. I'll mention the baud rate idea.

 

The car has had at least one, maybe 2, replcements while I've had it - I'll dig out all the old bills and see which was done.

 

Any other ideas ... ...

[Wullie 1]

Try here search.php?st=0&sk=t&sd=d&keywords=abs+resistance

[delfinis38 1]

I used a multi metre.... unclip each sensor socket and check the resistance. can't remember what they should be. the knackered one is the one with the lowest resistance.. you should get three readings that are approx the same and one low one.

[John-M 0]

I used a multi metre.... unclip each sensor socket and check the resistance. can't remember what they should be. the knackered one is the one with the lowest resistance.. you should get three readings that are approx the same and one low one.

That is exactly what I have just done, after reading the threads in the search results, ta for pointing me there, Wullie :)

 

Front offside was 'open circuit' - the other three all similar readings of about 0.'7 on my multi-meter resistance scale.

 

So off to see how much to get hold of a new bit now.

 

Thanks to all who helped :)

[JMC 0]

I bought my replacement one from ebay - £15 for a new Siemens one. Bit of a pain to fit, especially if the old one welds itself to the hub, but doable in an hour.

[John-M 0]

Damnit - got a genuine VW one just yesterday, considerably more than your Ebay price.

 

And yes, its a bugger to get the old one out. Had a go yesterday but didnt manage it. What method did you resort to, JMC ? I'm thinking I may have to remove the sensor ring and brake disc holder so I can get a drift into the area and use brute force.

 

But that'll have to wait a week, as I'm away.

[JMC 0]

Damnit - got a genuine VW one just yesterday, considerably more than your Ebay price.

 

And yes, its a bugger to get the old one out. Had a go yesterday but didnt manage it. What method did you resort to, JMC ? I'm thinking I may have to remove the sensor ring and brake disc holder so I can get a drift into the area and use brute force.

 

But that'll have to wait a week, as I'm away.

 

I chiselled mine out in the end while the hub and brakes were still on. I gripped the back of the old one and twisted in until it sheared the insides off from the metal outer casing, I could them pull it out. Then gently chiselled the metal ring in from the side of the hub until it folded in from itself and I could them pull it out with some mole grips. Be careful though - hit it too hard and you can push it into the ABS sensor. Took about 45mins of swearing in the end. Also with the new one if it's really tight to get back in gently sand down the shaft of it. If it's too tight and you force it you can break them.

[John-M 0]

Finally got this done, yesterday.

 

The old sensor was a real pig to get out - reckon its the original one and been in there since December 1994 !

 

It took some ( careful ) hammering and chisseling out with a screwdriver blade - and then the new one was very reluctant to fit.

 

Copious use of sandpaper on the insides of the mounting hole - and some slight sanding of the new sensor - and it was in.

 

Then found that the abs sensor ring was 'just' rubbing on the end of the sensor - it was slightly buckled - but got that straightened out by using the same screwdriver blade between the abs ring and the caliper mounting boss.

 

My abs light now goes out correctly - and abs is restored ( yet to be properly tested, lol. )

[C488ADO 0]

when testing with a multimeter yes you are correct looking fo rthe lowest resistance iirc you might need to turn the wheel to see if it changes the ohmage there is a whole section on this somewhere in the autodata website i used it several times on older cars ive had and saved me £££££ on hourly rates!

[greasegriff 0]

Have you got a link for your eBay sensor? Is it changed and working OK now?