[unkel]

Right. My '99 BMW 520i manual 2l petrol E39 had the ABS light lighting up, accompanied by the ASC light and at the same time neither speedo, odo or econo worked. This happened out of the blue one time and the issue has not disappeared.

After some internet research I reckoned the most likely cause was a failing ABS wheel speed sensor on the rear left side of the car. I procured one of them on ebay which my local mechanic fitted today and he reckoned the old sensor was deffo faulty. The ABS etc. light is still on. I haven't driven the car or tested if the ABS works though.

Here's my question: should the warning light have turned off after the new sensor was fitted or does the warning light only go off after you hook it up to diagnostics and switch it off that way?

[Stoolbend]

If the sensor was the only fault the light should go off once the car starts to move. A few metres should do it, but give it a couple of miles anyway.

If it doesn't go off after a spin you'll need to get it plugged in.

[ronanc15]

I know with Hondas and some other makes there is a very simple way to flash the ecu (pushing 2 prongs into a socket on the ecu). If this can be done with the BMWs it might be a better option to try that first before putting it on the diagnostics.

[Slidey]

Most ABS systems will reset once the car starts moving and the fault is no longer a 'current' fault.

You can always try disconnecting the battery for a few minutes. As I read your post my first thought was front LHS wheel as this is often the wheel that the speedo is taken from.

If the abs sensor can be adjusted closer to the sensor ring this may be the issue. The gap may be too large at the moment.

If not, the easiest thing to do is to find out if the fault code is definitely still on the LHS front. However it is not unheard of that the sensors have become mixed up before they get to the ECU, this means that the ECU thinks the front LHS when it is actually the RHS.

If they are 2 wire sensors a mulitmeter in the Ohm meter setting can tell you normally which one is faulty

[Drummerboy08]

Why did the speedo and associated clocks stop working too though? Surely the ABS sensor wouldnt have caused this?

[Andrew33]

Originally Posted by Drummerboy08

Why did the speedo and associated clocks stop working too though? Surely the ABS sensor wouldnt have caused this?

The ABS sensors do a lot more than just measure braking performance, they are also used in the traction control, speedo, odo and even tyre pressure(by measuring wheel rotations, a soft tyre will rotate more to cover the same distance as a correctly inflated tyre).

I'd say drive it for a bit and see what happens.

[Elessar]

Without wanting to get off topic I have almost exactly the same problem. BMW E46 320ci, the ABS/ASC lights keep coming on and then going off again after a while. I know the systems work fine because I only used them in the recent snow apocalypse (they started acting up before this).

I'm thinking the sensor/s are dirty? Might be the same problem for you unkel.

[RICARDO1982]

I fitted a NSR ABS sensor to my friends E46 BMW 2000 model i did not have a diagnostics and the light went away in 2 days and did not return . See how you get on.

[EnterNow]

As above, usually driving a few meters will do it. Ive seen one or two picky cars where the light only went out after a drive cycle (start, drive, off).

[Owen]

Pity you're not in Cork, I'd reset it for you. But try disconnecting the battery for a while, and then try turning the traction off and on to see what happens.

[Voodoomelon]

Originally Posted by unkel

Right. My '99 BMW 520i manual 2l petrol E39 had the ABS light lighting up, accompanied by the ASC light and at the same time neither speedo, odo or econo worked. This happened out of the blue one time and the issue has not disappeared.

After some internet research I reckoned the most likely cause was a failing ABS wheel speed sensor on the rear left side of the car. I procured one of them on ebay which my local mechanic fitted today and he reckoned the old sensor was deffo faulty. The ABS etc. light is still on. I haven't driven the car or tested if the ABS works though.

Here's my question: should the warning light have turned off after the new sensor was fitted or does the warning light only go off after you hook it up to diagnostics and switch it off that way?

I have direct experience with this on my E38, an identical system. The car does not have to move, let alone drive a number of miles for the dash lights to turn off. All you have to do is replace the sensor, turn on the ignition to position 2 wait for all the lights to go out and within a few seconds the offending lights just blink off.

The fact that your lights have not extinguished means its a different ABS sensor more than likely. Front and back are not interchangeable, however you can move them from side to side to diagnose the faulty sensor; in this case you can try moving the new sensor to the rear right wheel (assuming you still have the old one). Does your E39 have cruise control? The rear right wheel controls the cruise control system and if you have that option and it still works, then you know its a front sensor.

[Slidey]

If you check the resistance of the sensors it is a good way of finding a faulty one.

Normally when they are shagged you will have either an open circuit or a low ohm reading.

AFAIR most sensors operate between 50 and 150 ohms. I am open to correction on this

[unkel]

Thanks everyone for the help and suggestions

Originally Posted by barry81

If the sensor was the only fault the light should go off once the car starts to move. A few metres should do it, but give it a couple of miles anyway.

If it doesn't go off after a spin you'll need to get it plugged in.

My mechanic drove it for a mile. I haven't transferred insurance onto the car but once I will, I'll drive it for a bit and report back here. I've unplugged the battery for about 5 minutes but that made no difference.

Originally Posted by Voodoomelon

I have direct experience with this on my E38, an identical system. The car does not have to move, let alone drive a number of miles for the dash lights to turn off. All you have to do is replace the sensor, turn on the ignition to position 2 wait for all the lights to go out and within a few seconds the offending lights just blink off.

The fact that your lights have not extinguished means its a different ABS sensor more than likely. Front and back are not interchangeable, however you can move them from side to side to diagnose the faulty sensor; in this case you can try moving the new sensor to the rear right wheel (assuming you still have the old one). Does your E39 have cruise control? The rear right wheel controls the cruise control system and if you have that option and it still works, then you know its a front sensor.

I'm fearing you are right about that the new sensor should clear the light straight away. I've no cruise. I'm pretty sure that in the E39 the rear right speed sensor controls the cruise, and the rear left speed sensor controls the speedo. My car is of the earlier type with only the more basic ASC (and not DSC)

Originally Posted by Slidey

If you check the resistance of the sensors it is a good way of finding a faulty one.

Normally when they are shagged you will have either an open circuit or a low ohm reading.

Yes. But I've seen lots or reports of false positives of high impedance readings on the E39 with sensors that are ok - obviously I can't explain why

If the lights won't go off after driving it for a bit, I guess it is time for a diagnostic...

[El Guapo!]

I had a problem similar to this yesterday. (it was on a '06 320 though). The handbrake light was on (in yellow not red) and the traction control light was on. I put my diagnostic computer on it but it couldnt read the fault code
I noticed the front brake pads were fairly badly worn so I replaced them along with a new pad wear sensor. I knew it was a longshot but no harm in trying. Still the problem persisted.
I brought it to a guy I know in BMW and got him to put it on his computer.
Turns out the hydraulic control unit for the traction control and abs needs to be replaced.....to the tune of 2 grand just for the unit, with another 600-700 labour.
After he picked me up off the floor,... he said he'd stick in a good-will claim with BMW and see what happens. I should know by today or tommorrow.
OP hopefully this isnt your problem but just thought I'd put it out there in case anybody else encounters this problem.

[mickdw]

Originally Posted by Dean09

I had a problem similar to this yesterday. (it was on a '06 320 though). The handbrake light was on (in yellow not red) and the traction control light was on. I put my diagnostic computer on it but it couldnt read the fault code
I noticed the front brake pads were fairly badly worn so I replaced them along with a new pad wear sensor. I knew it was a longshot but no harm in trying. Still the problem persisted.
I brought it to a guy I know in BMW and got him to put it on his computer.
Turns out the hydraulic control unit for the traction control and abs needs to be replaced.....to the tune of 2 grand just for the unit, with another 600-700 labour.
After he picked me up off the floor,... he said he'd stick in a good-will claim with BMW and see what happens. I should know by today or tommorrow.
OP hopefully this isnt your problem but just thought I'd put it out there in case anybody else encounters this problem.

This is the most common fault on 3 series of that age. BMW are pretty much giving the part free in all cases. They will look for the labour though which is crap enough seeing as the parts are probably costing them F all from their supplier seeing as they appear to be faulty from new.