ABS sensor failure ?

[g8dhe]

Has anyone investigated what causes failure on the ABS sensors (error codes 11 to 14)?
I had an intermittent failure on my previous Bongo which seemed to be caused by moisture possibly in one of the connectors, however the problem would disappear after the first run of the day but would return next morning when parked on grass which had a lot of dew on it. Once away from the grass and dew the problem never returned.
Now however a similar problem has reoccurred on my current Bongo, similar effects but it returns to a fail mode much quicker I'm planning on replacing it shortly but would be interested if anyone has identified a problem, hoping to get my garage to retain the old sensor and cable for an inspection but would be interested in anyone else's experiences ?

[Hazzobongo]

All these ABS sensors are pretty much the same and though I've had no trouble with the Bongo ones I had to change them on the daughters mini which was recommended by a mini specialist mechanic when I changed the discs on that car. They're affected by all kinds, wet, dirt, stones bouncing up off the road, wiring corrosion, etc etc. It was a pig to do on the mini but seems simple enough on the bongo which I noticed while doing the front suspension, they're held in place on the suspension arm by one bolt, in my case very rusty and the head snapped off so had to be drilled out and its now back working wired and zip tied in place.

[Doone]

Hi Geoff. Maybe it's due to how they fit? I picked Allans brains. The sensors have an aluminium head and a plastic bottom. Inside, there's a magnet and coils of wire but no moving parts.
The front sensor fits through a hole in the wheel hub. That hole corrodes and the sensor becomes so tightly fitted that it breaks when removed. (The corrosion has to be removed from the hole, or the new sensor wont fit.)
The rear sensors fit into the axle and its oily. The hole doesn't corrode and they don't seem to display the same fault symptoms.

[g8dhe]

Thanks for the reports so far appreciated. Its just that the original style ones are getting hard to come by, and although there are a range of identical sensor units it would be nice to understand the failure mode. A simple break in the coil winding or its connection points I would expect to be a permanent failure, whilst at present I get a time delayed failure followed by a working sensor, which makes me suspect moisture in the connectors, in which case it might be a simpler fix to replace the connectors rather than the sensors themselves! However I couldn't get either of my front connectors apart, they probably haven't been disconnected in close on 20 years and I suspect that the plastic casings have degraded and "welded" together.

[Doone]

Apparently they usually come apart if you hold the clip and pull like crazy.

[g8dhe]

Yes, that was exactly my thoughts but neither side wanted to come apart! I might give them another try before handing it to the garage, however its rather frustrating to be thwarted by a blinking connector!

[sandoval]

Since the ABS sensor often reads from a magnetic ring integrated into the wheel bearing, bearing wear or failure can lead to incorrect readings. A worn-out bearing might have excessive play, causing the sensor to lose signal or produce erratic readings. When replacing the ABS sensor, inspect the wheel bearing for play or noise. If the bearing feels rough or loose, it may need replacement.