ABS problems

The time has come around to me having to sort my continuing ABS problem out (MOT pending) I wrote on this forum last year about paying £400 to have a new wheel sensor fitted at a dealers and it lasting a fortnight ( enough to get an MOT) and yes i know i should have taken it back.
Last weekend i removed the hub, stub axle and driveshaft. cleaned the inside of the swivel housing, the toothed ring and the sensor head. Re-assembled but still the light stays on.I am convinced that it is still be same wheel sensor thats giving me the problem

Can anyone tell me, how does the sensor detach from the wheel housing, is it just a rubber grommet with the sensor cable through the middle.
If i did manage to remove this how do i reseat it at the correct distance away from the toothed ring, or is it a preset distance (eg correct air gap) What should the air gap be ? Can i correct this fault without diagnostics equipment.

Its an intermittent fault - the dash abs light being on 95% of the time.
My 1996 Disco is great BUT I am thoroughly fed up with this problem

regards
Red.

If you understand the system it might help you find the fault. All sensors should have a small air gap, all should be the same. Nearly touching. If you have excessive wheel bearing movement the toothed wheel will push the sensor back causing a larger gap.

The ABS ECU measures an A/C voltage from each sensor as the wheels are rotating, a large air gap causes a lower voltage / no voltage hence the light comes on. The voltage is very low something like 2v.

Other possibilities are the difference in wheel size and tyre wear, ECU have a built in tolerance to over come part worn tyres.

Bad connections from the wheel sensor up to the ABS ECU can cause a resistance and low voltage getting to the ECU.
You can check the resistance of the ABS sensors, all should be the same, check them at the wheels and back at the ECU this will check the sensor wiring.
If all seems fine set the meter to A/C volts and spin the wheel you should get a low A/C voltage at the sensor wires, this also should be the same on all wheels. Broken segments the sensor faces is also a possibility.
And of course the ABS ECU could be faulty.

Hi All

I am interested to see where this thread leads as i have a similar problem on my td5. I have read other threads dealing with the dreaded '3 AMIGOS', to be honest alot of what is said is a bit over my head. Oh, my question is, where is the abs ecu, is it seperate from the main ecu, if so what does it look like?

And i agree, it is annoying seeing these three lights staring at u constantly!!!

Peter

Thx for your comments ETC 7867.

I'm not sure that excessive wear in the wheel bearing would make an affect because the bearings run on the stub axle which in turn is bolted to the housing. The drive shaft runs through the centre of the stub axle and I was wondering if the needle roller bearing and the bronze bush next to it on the stub axle wears at all or is something that does have to be replaced from time to time. Any comments welcome.

just check all the sensors are pushed in - when you drive they 'knock out' to the correct distance. i just tap them in with a screwdriver and mallet VERY GENTLY as theyre bloody expensive to replace.
Only other trouble is if a wheel bearing is knackered - which it wil fail MOT on anyway.
There is a way of getting the error codes to flash using the ABS light - have a forum search and youll find it - involves a paperclip.
I really hate ABS too!!!!

Alright folks.I had the same problem on my '95 300Tdi and i ended up removing the ABS bulb and fuses as it seemd a lot easier than getting to the bottom of the problem! I know it's a last resort but it passes the Mot and gives you one less thing to worry about! Bye for now.

I tried the pull the light and fuses trick (on a classic RR). Instant MOT fail, the bod said that the ABS light should come on at startup then go out when you move off. It didn't so it failed....

richcrazy said:

Alright folks.I had the same problem on my '95 300Tdi and i ended up removing the ABS bulb and fuses as it seemd a lot easier than getting to the bottom of the problem! I know it's a last resort but it passes the Mot and gives you one less thing to worry about! Bye for now.

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Hi Guys, I took my 98 300tdi in for its mot some 3 weeks ago knowing full well that with the ABS light on permanently it would fail the MOT. However much to my surprise my garage passed it no problem? I didnt push it as I thought it may have been an oversight on their behalf, they advised me that as the pads were low on the rear disks they put it down as an advisory and passed it. Now we all know the disks have nothing to do with the ABS sensors.

Have I got stupid garage? or has my luck changed?

Wen I got it home I just did as I usually do and remove the fuse and back to safe braking again. got used to the light being on, makes a chang n e way as im used to at least 2 or 3 being on usually.

Not much help I know but if you live in th Southport area may well be worth taking it to my garage!

Well if it was me, I'd keep using that garage for MOTs.....but not much else!

redhotmax said:

Thx for your comments ETC 7867.

I'm not sure that excessive wear in the wheel bearing would make an affect because the bearings run on the stub axle which in turn is bolted to the housing. The drive shaft runs through the centre of the stub axle and I was wondering if the needle roller bearing and the bronze bush next to it on the stub axle wears at all or is something that does have to be replaced from time to time. Any comments welcome.

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You are right,also if the swivel bearings are slack it will have the same effect.Only the rear sensors are effected by the wheel bearings.(On RR classics and Disco 1's)

Sparks said:

Well if it was me, I'd keep using that garage for MOTs.....but not much else!

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I don't do all me own repairs, least know theyre all done proper, even the little independants rip the daylights out of ya if you dont know wot ya doin, give em an extra tenner and jobs a gud un! 10 notes a year can't whack it!

I am visited by the three amigos every day, it is at exactly the same place in my morning journey after driving for approximately 15 minutes. I exit the motorway and coast quarter of mile to traffic lights, as I hit the brakes they light up.

If I turn the engine off and restart holding brake pedal down I can usually drive for another 30 miles to work without seeing them.

The ABS light on my '94 Discovery has been on for at least three quarters of the time I have owned it. It hasn't been on for 3 weeks now which I thought was a blessing as it had MoT on Wednesday.

Bloody thing came on during test and so failed!

*curses*

Unfortunatly that wasn't only thing it failed on though...

so let me get this straight... I take all four wheels apart......

you know what .. i am stuck... my ABS light has been on since I bought the ()*&*( thing and it is winding me up... the guy who sold it to me seemed genuine so when he told me it was a sensor and they were £25 each I took his word for it... now I am told could be £400 to fix but wont know until I pay £55 +vat to find out what's wrong with it by plugging in to the ecu...

can someone help me out..

sorry this may be my first post here although I registered ages ago but I am really struggling with searching the forum....

See my posting on this forum here - http://www.landyzone.co.uk/lz/f8/300-abs-light-27043-4.html

It may not be a sensor problem - but if it is it probably just needs knocking in. The chances of it being broken are pretty low.

With regards to MOT's it looks like taking the bulb out might get you through - but mine had been removed by a previous owner and it failed mot on abs light inoperative. However, here in Northern Ireland all MOT's must be done at goverment test centres and they have big computers with all the correct tests!

Once you've sussed out how to reset a fault in the computer its very easy to find the fault. The chances are it will be a sensor and it takes about 20 minutes to fix (18 of which are jacking and taking off wheel).

If you have any questions post here or I think you can send private messages - sent me your number and I'll give you a ring.

BTW I have my mot in at 18:45 tonight!

Stuart

First thing to do is get a blink code out of your ABS ECU and find out what the ECU thinks is wrong. Clear the fault code memory down, take it for a spin and when the light comes on again see what triggered it.

You might also want to try removing all the relays and fuses and making sure all the connections are good and clean. An iffy relay will cause the warning light to come on as would a dodgey earth or dirty connections. Is there any evidence of damp/condensation in the area around your ABS ECU?

I know the ABS on my RRC is a bit twitchy sometimes and I believe the Disco is no different.

A friend of mine had a recurring problem where one wheel sensor kept moving and making the air gap too large, he tried burring the top of the hole and even putting superglue on it but it wouldn't stay put. In the end he disconnected the warning light and carried on as normal with no MOT issues I know of.

classic kev said:

You might also want to try removing all the relays and fuses and making sure all the connections are good and clean.

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Get the code first- removeing the fuses will cause the computer to record more faults so it takes you longer to find the real one!

mjltigger said:

so let me get this straight... I take all four wheels apart......

you know what .. i am stuck... my ABS light has been on since I bought the ()*&*( thing and it is winding me up... the guy who sold it to me seemed genuine so when he told me it was a sensor and they were £25 each I took his word for it... now I am told could be £400 to fix but wont know until I pay £55 +vat to find out what's wrong with it by plugging in to the ecu...

can someone help me out..

sorry this may be my first post here although I registered ages ago but I am really struggling with searching the forum....

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You really need to plug into a diagnostic computer as there are several parts that can go faulty and cause the light(s) to come on. £50 + vat seems a bit steep tho and you need to replace the wheel hub and sensor rather than just the sensor. Cost me £250 to have it done recently and no lights since. Whereabouts are you as I can highly recommend a Land Rover specialist in north Manchester

well thank you for your help.. I have owned the disco for a few months now and this is the best source of info for this type of fault I have found... so blink test and only one fault code.. 2-6.. so that is apparently

2-6 (BPP)Brake pedal position switch

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and as I had that or something like it replaced a couple of months ago when the brake lights stopped working I figured let's go for a drive...

so start the engine, pull away and the light goes out for the first time since I owned the car... only a short spin but hard on the brakes many times and no reappearance of the light...

saved a fortune, feel brilliant... but miss the friendly orange light on my dashboard now....

If you haven't already - what you want to do now is clear the stored fault from the memory - by removing the link and putting the relay back in and then turning the ignition off and on again during the blink test.

That way on start up you'll get an on-off-on which will go off again just down the road.

If the light does not blink off - but still goes off when you drive away - it means there is a "stored fault" - i.e. one in the past.

Despite me clearing all the faults last week I noticed yesterday I did not get the off blink on start up - read the code and got a 2-3 (inoperative pump). I just cleared it. I reckon it was a glitch.

This makes it much easier to diagnose a real problem!

My mistake was - once having found the full list of codes - was to try and fix the first one by removing testing all ther relays and all the connectors! This caused about 15 faults to register.

I reckon I cauld get the blinks up and cleared in my sleep know!