Brian Moooore ABS FAULT

[TW166Y]

Hi Brian,

i was installing speakers the other day at the front and as you are aware you have to dismantel the glove box to get the kick panel off... while i was there i noticed the abs ecu, yes? anyhow i removed the plastic cover and the the ecu plug was "unplugged".. i thought wierd.. plugged it back in and now my problem is the abs is actually kicking in nearly every time i brake even at slow speeds... do you have any idea's what this problem could be? thanks buddy Pete

[Jon_Bmw]

Nice of the previous owner to disconnect it

Right pete, explain what happens from when you turn the car on.

Does the light come on when you have the ignition on

Does the light come straight on when you start the car.

Does the light come on when you start moving about 5 miles an hour

Does the light not come on at all, and does it make a crunching noise without any effective brake performance.

Answer those questions and we should be able to see you right

[Jon_Bmw]

Just read another post, identical to yours, bar simon13's is in the latter stages of a abs sensore fail. Read this post pete, follow brians explanation.

http://www.e30zone.co.uk/modules.php?na ... highlight=

[Brianmoooore]

Ehm! Something different!
All I can think of, is that one sensor, although OK in itself, has a low output, just on the margins of what's needed to keep the ABS happy, and, as you're driving, the output drops off when you brake, and the ABS interprets this as a locking wheel.
Check the sensor resistances first, as that's easy to do, then check all the sensors are properly in place, and all the sensor rings are clean.

[gcorky]

ditto,see twiggy you doubter...lol

[Jon_Bmw]

Ehm! Something different!
All I can think of, is that one sensor, although OK in itself, has a low output, just on the margins of what's needed to keep the ABS happy, and, as you're driving, the output drops off when you brake, and the ABS interprets this as a locking wheel.
Check the sensor resistances first, as that's easy to do, then check all the sensors are properly in place, and all the sensor rings are clean.

Brian this was how my problem started many months/years ago, very worrying as you get no braking effort!!

It eventually progressed into the problem that simon13 is posting about now, one second hand abs sensor later, problem solved.

[TW166Y]

ditto,see twiggy you doubter...lol

So where are the sensors actually located fella's...

the problem i get is i can be parking up outside my house "on dry tarmac"... just simply reversing into a space and pulling forward etc... not even doing 5mph out and i can feel the abs through the pedal and hear it kicking in on the passenger side... like a crunching noice as described above... all check lights work to say brakes are ok, i just want to get it sorted or else it will be another job that has to be stuck on the "jobs to do list"

[Jon_Bmw]

ditto,see twiggy you doubter...lol

So where are the sensors actually located fella's...

the problem i get is i can be parking up outside my house "on dry tarmac"... just simply reversing into a space and pulling forward etc... not even doing 5mph out and i can feel the abs through the pedal and hear it kicking in on the passenger side... like a crunching noice as described above... all check lights work to say brakes are ok, i just want to get it sorted or else it will be another job that has to be stuck on the "jobs to do list"

Well this is what mine was like in the early stages of an abs sensor failing. Do the resistance check that brian has described in the other thread and I think you'll find one is lower than the other. Come back to us with your findings pete.

Edit: location: Front two sensors come in through the inner arch, passenger one runs along the top of the chassis rail iirc. Look for the little yellow mouldy coloured connectors, disconnect and shove you multimeter in the wheel side of things. The drivers side runs up near the relay box(little plastic cover on it) again iirc.

[Brianmoooore]

ABS shouldn't work at all below about 10MPH. The ABS computer uses the signals from the wheel sensors to determine speed completely independantly of the speedo signal, so maybe it's interpteting a noisy signal from a sensor as a road speed of more than 10MPH.
Can you tell which wheel the ABS is backing the brakes off on?

[TW166Y]

thanks guys...

cant tell which wheel is trying to brake, i just hear the crunching and feel the pedal.... but as you say abs shouldnt kick in untill after 10mph soo somthing is a miss... ill buy a multimeter and give it the once over.. thanks everyone for your help