Golf VR6 Mk3 ABS light problem

Dunno about the Golf specifically, but in a general sense the wheel sensor is usually something like a ring of magnets set into the hub next to the bearing so that the magnets turn with the wheel, and as they pass a fixed coil in the hub, they generate a pulse of electric current.

These pulses travel up a pair of wires to the ABS module which takes in information from all four wheels and then controls the ABS pump, which can be combined with the module to form an ABS unit or to be separate units.

Because it is logical to position the moving and non-moving bits around the bearing, when the bearing starts to go it is normal enough for the movement in the hub to involve the destruction of the magnetic ring shortly afterwards.

So the easiest thing to do first is jack up the wheels and see if any are wobbling about indicating a bearing has gone, if so then you ought to replace both bearings on that axle and both sensor rings if they're not too expensive. It's mostly labour. It's quite likely that the fault will lie in the wheel with the bad bearing so with any luck that fixes the ABS problem.

If you're into diagnostics more than mechanical trial and error, putting an oscilloscope or sensitive multimeter onto the wires and spinning the wheel may tell you which one is electrically different, and indicate which needs changing, although as I say if the bearing is shot the new sensor ring will get damaged pretty quickly too.

The ABS module part is quite expensive compared to sensor rings or wires, however it is trivial to replace (generally speaking). By contrast, troubleshooting the wheel sensors is heavy on labour so garages are more inclined to put you to the cost of an ABS module (with their margin on top as their profit for little effort) and to worry about the sensor rings if that doesn't work.

There are also devices for asking the ABS module why it has failed safe. It will know it is because, for example, there is an intermittent signal from the rear left wheel, indicating the sensor there rather than a break in the wiring. If the garage has the right kit, diagnosis is quite straightforward.

Hope this helps.

It's usually caused by a fault with one of the ABS sensors. When the light comes on, the ABS system fails safe so your brakes behave just as they would as if no ABS was ever fitted. I also think it's an MOT failure.

What can happen is dirt and swarf (sensors are magnetic) from the brakes can make the sensor give strange readings to the ABS system, so it fails safe and registers a fault. This is manifested by the light on your dash and also by a code accessible using specialist equipment from the diagnostic port of the ABS system. I don't know what the code says, probably just which sensor is down, or is it's something more serious than a sensor (unlikely), details of that.

It's also possible that the sensor has just died through old age and/or heat damage from the brakes. In this case, the same result as above as regards fault reporting.

Firstly, take off the wheels and give the sensors a good clean with brake cleaner - they're black plasticky things mounted in the area near the hubs (you'll see a toothed ring around the hub - the ABS sensor faces these and calculates the speed of each wheel using the toothed ring so clean out the notches of the ring too).

If you still have a problem, find the connectors inside the car for the ABS sensors. Follow the wire from the sensors up through the car until you find where they connect to the ABS loom (these are tubular white/off white or yellowing connectors).

The front ones are sometimes located near the suspension turrets under the bonnet. The rear ones are often under the rear seat or somewhere around the rear suspension turrets.

Disconnect them by squeezing near the tabs and you'll see the prongs that make the electrical contact. IIRC the female side is the sensor side, so use a multimeter to measure the resistance of each one (set the meter to the most sensitive setting). They should all return a very similar, static reading. If one of them is wildly different to the others, or the reading won't settle down and keeps changing, you've found your duff sensor.

If you need a new sensor, they're made by Bosch. VW will charge you about double what a Bosch dealer will (but it's wise to get a price from VW just in case). Go to

and click theDealer Locator link. Have detailed specs of your car ready and spendwhat you saved (you're looking at at a saving in the region of =A350 persensor) on getting a local garage to fit the new sensor (In myexperience it's very hard to get the old ones off). Or, you can take the ABS dash light out and hope that the MOT man won't notice ;) Hope this helps

The message from snipped-for-privacy@quickwatchsales.com contains these words:

Just iron teeth. No need for magnets.

& by the time a wobbly wheel bearings let it come into contact with the sensor you'll have gone deaf from the noise.

Your experiences may differ to mine, but I've seen four failing wheel bearings lead to ABS fault lights on four separate cars and in each case, the magnetic sensor ring was scrap. I doubt faulty ABS sensor rings cause the bearings to fail, so I prefer to interpret that as faulty bearings causing the sensor failure.

This page gives a good description:

Obviously not all ABS systems are identical, and I dunno what the Golf has, although it will be broadly the same.

Well on the Golf if you ignored the vibration/noise for long enough the sensor could shake loose & touch the ring. However if you where dumb enough not to notice that then you'd never notice a pretty ABS light. I suppose somebody might have made a car where the wheel bearings would allow significant motion without making noise but I've not met one, which ones have failed on you?