Got the ABS light on permanently in my wife's 52 plate 1.2 polo.
Guess its time to replace the sensors, and looking at some pictures of them I think it may be something I can do, or am I courting disaster?
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ABS sensor replacement, easy?
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Posted 10 months ago #
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I'm not familiar with ABS on cars, but on trucks and buses I wouldn't just replace all four sensors hoping that that would cure the fault.
First of all, check each sensor.
Unplug each one and check for resistance across the two pins.
I don't know what the correct figure is, but as long as you've got some resistance, not an open or short circuit, it's probably OK.
Next, spin each wheel and check for an AC voltage output at each sensor.If that doesn't trace it, check the exciter rings.
Again, I don't know about cars, but on some trucks they are built in to the discs.
They can go rusty so the rust fills the gaps between the segments so that the sensor doesn't recognise that the wheel is turning.
Remove the disc if you have to, then scrape the rust out until you have got clearly defined segments.Posted 10 months ago # -
You need the fault code to see which one as they can be up to or over 50 quid a piece.
Really easy to replace tho, usually just 1 bolt or allen key/torx.
Check the surface it sits on for any crap, and if it has a sensor ring (cog looking thing round the cv joint or in the brake disk) check for any damage, it is inside the bearing on more modern VW/Audis tho.
The fault light might not go out straight away, give it a run first and try to get the abs to kick in on gravel, then take the key out of the ignition and start the car again.
Posted 10 months ago # -
You may find one of the exciter rings has split,this appears to be a common problem rust gets underneath the ring expands and splits said ring.
If this turns out to be your problem dont let anyone sell you a new drive shaft as they can be repaired.
You will need to remove the drive shaft to carry out the repair.
Take the ring to a good welding shop and get them to tig it back together for you,give the ring mounting a real good clean and refit the ring using 638 loctite.
I have repaired 4 or 5 using this method and it saves a small fortune with not having to purchase any parts.
Where are you based?Posted 10 months ago # -
Thanks for the info everyone. It might be getting a bit more technical than I'd hoped. I'll take it to the dealer and get it on their computer and see if it spots which sensor is faulty. I think I'll be ok replacing a sensor but any talk of drive shafts etc will be a bit beyond me unless the haines manual does a good job of it.
dadandlad, I'm in Ashford, Kent.
Posted 10 months ago # -
dadandlad....Any on-line diagrams?
Posted 10 months ago # -
One other Q. This polo has disc front and drums rear. Will there be abs sensors on the drum brakes too?
Posted 10 months ago # -
There will be a sensor for each wheel.
MTG, most car sensors havn't been inductive for a good few years now, so doing what you suggest won't yield accurate results.
Two wire Hall effect sensors are much more common now, and rely on having a constant voltage wire (some are 5V, but some are at battery voltage), which is then switched. Easiest way to test them is with the sensor still connected, and using back probe adapters on the vehicle loom side to check the voltage is switching, as the wheel is turned slowly.As for changing them, in theory they're easy. But in practise, on something a few years old, they may be rusted in. Only way to get them out then, is to destroy them, and then spend a bit time cleaning the hole so the new one will slot in and locate without any force (if it needs force, or doesn't locate by hand pressure, then you risk damaging the new sensor).
Dadandlad, technically it's either an inductor or reluctor ring depending on the type of sensor, but they're more commonly referred to as ABS/pulse rings. However, when you can get CV joints for less than an hours labour, they're not worth repairing, and that's before you consider the whole insurance liability risk which is becoming an ever increasing issue.
Besides, pulse rings are becoming less common, as manufacturers move to striped magentic bearing seals (they do have a proper name, but I've forgotten!)Posted 10 months ago # -
This just happened to my friends 07 golf. Seemingly it is a known fault on VW's. There is a repair kit available for the golf that is about £500 plus another £90 for diagnostics. As is a known fault he is trying to get VW to pay some of the bill.
Not sure if this is the same for the polo. Have a look on some of the car forums, that is where he found out that it was a known faultPosted 10 months ago # -
they can be up to or over 50 quid a piece.
Tell me about it. One has just gone on my Honda, £200 each! And they think both the rear ones have gone.
Posted 10 months ago # -
worth spending the money on someone with the right fault code tool.I took the pug to a garage and he reconed the rear nearside was at fault.I bought a new one and it didnt solve it.It was something else.
On the other car it turned out to be the connection at the abs/brake pump under the bonnet.That was after the garage thought both rear sensors were at fault.(200+ quid a pair before splashing out on a 2nd hand abs unit)
changing them is easy.the time cleaning up the rust etc around them can sometimes be where all the time goes so maybe have a look around first to see if the rings on the hubs are looking a bit odd.also make sure they are clean and plugged in correctly.I sprayed my connections with acf50 before refitting to try and help them survive the winter.The flat bladed connections on one of the leads turned to powder so its worth putting something on them before fitting.
*or unplug them and do it yourself once you get it back from the garage.. as theres no way they will be doing it!
Posted 10 months ago # -
Oh dear.
Just got back from the vw dealer. Sat there for 2 1/2 hours waiting for them to run the diagnostics. Told I might want to sit down a bit longer as the diags picked up a dead ABS control unit/hydraulic pump.
£1100 pounds please! Not a known fault and not something they have seen before on a polo of that age.
Scrapyard challenge?!Posted 10 months ago # -
phew!
Posted 10 months ago #
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