Hyundai i20 ABS light on

[Mottie]

Another type of fault, is a 'Dynamic ABS fault'. The light comes on to prove it works, goes off, then as you drive away, the ABS light comes back on and remains on. That suggests, the controller is seeing the sensor at switch on, it seemed to work, but the pulses on the output, are not in line with what it expects. That could be that the magnets in the ring, have some rust, sticking to them, or similar.

I had that on a Mondeo once. I only changed the front wheel bearing but had all sorts of abs/traction control problems immediately after. The car was undriveable with brakes locking on, warning lights etc. It was a pattern part and on Mondeos, the ABS magnets are built into the wheel bearing. Fitting an OE bearing at three times the price cured it. Didn’t need to reset the light on them, just drove it down the road and the light went off.

 

[gemshan1]

You are being unreasonable. All that a scanner can do, is indicate the correct corner, which the ABS controller is reporting as being faulty. Beyond that, it is down to the mechanic, or who ever is assigned the repair, to further diagnose it, down to the actual point of failure.

If your ABS system is similar to my own. Then in the wheel hub, is a metal ring, with maybe 50 magnetic points around the edge. Your sensor will be an Hall Effect switch, basically a solid-state, electronic item with three wire terminals, +ve, -ve, and an output. Every time one of the magnets, passes the Hall sensor, the output terminal will flick on and off. If you spin the wheel slowly, you can see the output pin change, with a multimeter.

You can also test a sensor, without installing it, by plugging it in, connecting a meter, and waving a magnet in front of it.

Those +ve, -ve and the output, have to get back to the ABS controller, if they don't, due to damaged wiring, the system will flag an ABS fault. A 'static ABS fault', where the light comes on with the ignition and remains on, even if you do not move the vehicle.

Another type of fault, is a 'Dynamic ABS fault'. The light comes on to prove it works, goes off, then as you drive away, the ABS light comes back on and remains on. That suggests, the controller is seeing the sensor at switch on, it seemed to work, but the pulses on the output, are not in line with what it expects. That could be that the magnets in the ring, have some rust, sticking to them, or similar.

Hey I’m not being unreasonable, I’m paying a “technician “ who says he can fix the problem… he can’t ?!!!!!!

 

[freddiemercurystwin]

You never gave him the opportunity to fix it. You decided to change the part yourself, so that's all on you.

 

[Harry Bloomfield]

Hey I’m not being unreasonable, I’m paying a “technician “ who says he can fix the problem… he can’t ?!!!!!!

You were paying a technician, to try to put the light out, you say he added 'he says what if he can’t turn the light off?'. In other words, he was asking you if you wanted to go ahead, knowing there would be a £55 charge, irrespective of whether you had fixed the issue, or failed to fix it, and the light thus could not be turned off.