Tripod Posted April 5 Report Share Posted April 5 My lupo GTI has been very good to me but I recently had a N/S front ABS fault, which came up as faulty sensor. Sensor was replaced, code cleared and all apparently working fine. Today I took it in for MOT then got a call from garage saying that, when front wheel is on rolling road, the N/S front brake is engaging slowly until locked and ABS can be heard. Even with feet flat on the floor! Other observations noted were: - doesn't happen on open road, when all 4 wheels are turning - doesn't happen on rolling road if ignition is off - N/S pads worn at about twice rate of O/S - no fault codes - not had any noticeable braking difference, pulling to one side under braking etc - no random ABS engagement in day to day use - ABS has been functioning as it should on the road before and and after ABS sensor fault - I have occasionally smelt hot brakes but figured it was just my driving... guess it could have been the the N/S front though Figured it could be the new sensor was faulty but that should throw up a code. Currently thinking maybe ABS module but no idea really. Any thoughts would be greatly appreciated. Quote Link to comment Share on other sites More sharing options...
Tripod Posted May 20 Author Report Share Posted May 20 Does anyone know if the ABS unit is coded to the car? 51 plate. Quote Link to comment Share on other sites More sharing options...
mk2 Posted May 20 Report Share Posted May 20 Have the coding rings (the metal ring on each hub which generates the pulses) ever been replaced? I wonder if the coding rings are the same on each wheel... have any hubs ever been replaced? Or maybe even the speedo sender or gearbox? The ABS relies on all input data being in 'tune' with each other. If anything is non standard / different, you could get weird behaviour. Quote Link to comment Share on other sites More sharing options...
Tripod Posted May 20 Author Report Share Posted May 20 (edited) The rings and hubs haven't been replaced in the 10 years I've owned it, so I assume they never have (on 165k). They look in pretty reasonable condition too, I gave them a quick wire brush and no flakes of rust, just fine dust. No visible cracking either. I have replaced both sensors, I've booked it back in to the garage for further investigation and asked them to check resistance in the cables. Most of the obvious issues should throw up a code.... I got codes for both sides when sensors disconnected. Also made sure all of the engine bay fuses were pushed in properly as aware they cause some peculiar issues. I'll give the contacts a proper clean later. Utterly bamboozled by this one. How does it get gearbox info? Sensor? Where? Edited May 20 by Tripod Quote Link to comment Share on other sites More sharing options...
mk2 Posted May 20 Report Share Posted May 20 Speedo pickup... I think it somehow compares overall car speed with differential wheel speed. If something is different, it could cause unusual ABS wheel behaviour I'd guess? Quote Link to comment Share on other sites More sharing options...
Tripod Posted May 21 Author Report Share Posted May 21 Will suggest this to garage as something to think about, thanks. Quote Link to comment Share on other sites More sharing options...
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