Will ABS/DSC lights turn themselves out when the fault's fixed? - EDIT: Yes they do

[Lazlo Woodbine]

As per the title. My ABS and DSC lights are on constantly, they come on with the ignition on check and never go out.  "DSC system fault" shows on the screen 9/10 times. I have only occasionally not had it appear and when it doesn't I can turn DSC on and off as normal but ABS light stays on.

I bought the car two weeks ago knowing it had a fault, the previous owner only used it occasionally and a few weeks ago he went to drive off only to find the brakes stuck on. He unstuck them by just driving away and that's when the lights came on. The o/s handbrake is useless so my hunch is that it was the sticky one.

Cruise control works but I don't know which wheel speed sensor it uses.

I had a local garage use their Solus scanner on the car last week but my battery voltage was too low for the scanner to communicate. I have since replaced the battery as a matter of course since two days on a smart charger wouldn't revive it.

I now have a collection of used ABS sensors, front uprights c/w hubs and the ability to test and fit them so was hoping to save paying for use of the scanner. I also have four callipers and a spare ABS pump c/w module just in case.

So yes is there anyway to reset the DTC once I fix the problem? As it is I can test individual sensors, the reluctor rings and probably the loom back to the ABS/DSC module but if it's none of them and the codes won't reset themselves I'll be stuck with repeated scannings and paying for the pleasure.

PS. I did buy a Maxiscan Vgate VS890 which was recommended (on this forum no less) and advertised as doing ABS codes, it doesn't..

 

[Tigger]

Hi Ralph,

if it were me, I would look at the discs, brake fluid, pads etc and replace accordingly, do you know when any of the aforementioned were replaced or serviced  ? Sensors are well known for being sensitively difficult with the slightest anomaly, sorting these should allow a reset,  I've just had all my disks, pads and fluid changed and all is well. It could well be a mechanical issue that is setting the D.SC.  / abs light OFF.

Cheers

Andrew

[Lazlo Woodbine]

Thank you for the input but it's the matter of the fault codes clearing themselves without the use of a scanner that I need to resolve. I've got a handle on the mechanical side of things but OBD is new to me.

Today I made an LED test light rig to test individual wheel speed sensors and found two (both o/s) which I have replaced with good used ones. Now that I know the colours of the wires leading to the ABS/TSC module I shall use the same rig to test the loom between the plug into the module and the sensors. Once I've got this issue sorted I'll try and find time to do a write up on making the test rig and how to use it, it's no OBD scanner but it cost under a tenner and actually allows you to do things a scanner won't.

The burning question still is whether I need to plug the car in to clear the DTCs which the ABS light tells me must(?) be there. Due to a stupid error the car is still on stands tonight so I haven't had a chance to find out yet. Once it's running I suppose I can use it till Saturday and if they're still there I'll have it scanned.

That error, yes.. The o/s/r caliper seemed to be working on the footbrake but not the handbrake, not at all. So I had a look at the two calipers in that pile of used parts I mentioned above. One was nice and shiny with a smooth handbrake cam, the other was seized up with burst seals and a rusty piston. Guess which one I needed.. yes the knackered one. No problem! The only difference left to right seems to be the handbrake arm and cable bracket. I'll just swap them over and Bob's your mothers brother. This was great until I fitted the newly fettled shiny caliper and realised that the bleed nipple was at the bottom, below the hydraulic line, meaning it would have to come back off for this and every subsequent bleeding. Swearing commenced followed by packing up and putting the kettle on.

[Lazlo Woodbine]

Well I rebuilt the original o/s/r caliper and fitted that today. Simple stuff really, just wind the threaded piston out, remove a circlip and the whole handbrake cam assembly comes out in one piece. Muck had got past the external seal of the shaft that the handbrake arm fits to made it all rusty. The piston and its seal were in good condition so I cleaned that up the handbrake gubbins and reassembled it. I now have a working handbrake, which is nice. I may bebuild the knackered spare caliper with new seals just for fun..

So having got the car back on its wheels and knowing I had four working wheel speed sensors I disconnected the battery and went in for a cuppa. Half an hour later I hooked it back up, ABS light on, but no DSC warning and I could switch it on and off, encouraging. I figured it was wiser to have it scanned now and reset the light rather than risk the light staying on becauseit wouldn't reset itself or worse there was another fault (MOT on Monday). So I set off to collect the ball joint I'd ordered and go to the garage. A mile or so down the road the ABS light went off! Despite repeated re-starts it won't come on, fantastic! Not so fantastic is the tickover now stays at whatever revs you were at when dipping the clutch. Sometimes it will drop back, sometimes not. I've told myself it's the ECU trimming up after the lack of power..