ABS warning light

[Alan W]

Hi, new owner / member with a 1999 Roadster 2.8 auto.

Just before the car it had a fault which was rectified just prior to purchase. The ABS warning light was on and a diagnostic check showed rear ABS sensor so both were replaced and the problem was solved..... for about a week. Now the warning light comes on about 20 minutes into a drive and at other erratic times. One mechanic told me that this was common and can be caused by a short in wiring between the sensor and the ECU and the only way of eliminating this as a possibility was to remove the entire interior (sets and carpets) and to inspect the wire.

Is this a common fault or is it a fault with many possible causes?

[Brian H]

Hi Alan,

Have you had the fault codes read recently to establish the fault? there are a number of things which can cause the light to come on so it would be difficult to guess.

.........One mechanic told me that this was common and can be caused by a short in wiring between the sensor and the ECU and the only way of eliminating this as a possibility was to remove the entire interior (sets and carpets) and to inspect the wire.

Whilst a being a member on here I have not heard of the entire interior having to be taken out for this type of fault before.

Brian

[BladeRunner919]

Whilst a being a member on here I have not heard of the entire interior having to be taken out for this type of fault before.

Brian

Nor me. But if I was a mechanic being paid by the hour...

[Del]

This thread might throw some light on the matter
http://www.zroadster.net/forum/viewtopi ... 79#p350679

[Brian4]

I would say it is unlikely to be a short under the carpet but more likely one of the plugs for the rear sensor is not fully pushed home when replaced and has damp in it or is just loose and move slightly as the car is going along.

Our fault with the DSC system was down to worn control arm bushes on the front allowing the front wheels to move and upsetting the steering angle sensor on the steering column. Those cars with just ASC do not have the steering column sensor but just rely on the 4 wheel speed sensors.

[Robert T]

What is the build date of your car? 1999 could put it either side of the facelift. Or put more simply, does it have an ASC or a DSC button? ASC has less components that you need to look at.

Is the yellow ASC/DSC light also on on the dash or just the ABS? They frequently come on together, as there are a lot of common components. Not sure if it will shed any light on the problem, but it is useful to know.

I would have thought if the wiring loom were to fail anywhere it would be on the outside of the car where it is vulnerable - more than likely close to the connector for the sensor. There are very few other places where it is free to move and could chafe. For pics of the connector see: http://www.zroadster.net/forum/viewtopi ... =5&t=17295

Cheers R.

[Alan W]

What is the build date of your car? 1999 could put it either side of the facelift. Or put more simply, does it have an ASC or a DSC button? ASC has less components that you need to look at.

Is the yellow ASC/DSC light also on on the dash or just the ABS? They frequently come on together, as there are a lot of common components. Not sure if it will shed any light on the problem, but it is useful to know.

It is a 1999 reg and guessing that its the facelift car as l was told that on this model the rear wheels are wider track than the front and this was an alteration BMW made and to accomodate this the rear wheel arches are bigger? Iam fairly sure it has an ASC button and when you turn this on the main fault/warning illuminates.

[BladeRunner919]

It is a 1999 reg and guessing that its the facelift car as l was told that on this model the rear wheels are wider track than the front and this was an alteration BMW made and to accomodate this the rear wheel arches are bigger? Iam fairly sure it has an ASC button and when you turn this on the main fault/warning illuminates.

Does it look like this from the back (pre-facelift):



Or this (post-facelift):

[spanwah]

similiar issues on my 2.2 got the fault code which was faulty pump went on ebay bought second hand pump(29 squiddley) just for the electrical side(black box attached) as mechanical side feck all geos wrong! 2 screws and 5 minutes later swapped over hey presto everything works and touch wood never had a issue again!!!!
first port of call fault codes read!!!!

[Alan W]

Just compared the car to the above rear end photos and it is a facelift and it has ASC.

Is the yellow ASC/DSC light also on on the dash or just the ABS? They frequently come on together, as there are a lot of common components.

The ASC warning light comes on with the ABS lights.

Also,when I turn the ASC on the ASC light on dash illuminates - is this light just to let you know that ASC is on - or is this saying there's a fault?

[Jonco]

Also,when I turn the ASC on the ASC light on dash illuminates - is this light just to let you know that ASC is on - or is this saying there's a fault?

Wrong way round I think . ASC is on by default on ignition start. If you press the button then light comes on to warn you it is off.

Have a look at this http://www.zroadster.net/forum/viewtopi ... =5&t=38176

[Alan W]

Thanks Jonco - that makes sense

[Alan W]

The ABS warning light was on and a diagnostic check showed rear ABS sensor so both were replaced and the problem was solved..... for about a week. Now the warning light comes on about 20 minutes into a drive and at other erratic times

This is wierd, this fault now appears to have completely rectified itself of its own accord?

[henrycrun]

Can anyone suggest reasons why ABS and DSC warning lights are so temperamental ?
Mine have been lit since Christmas. Today the've gone off.

Do I bother to investigate (ready for the MOT) or just cross all fingers on the day?