ABS Issues

[skibo]

I've searched the forums for ABS but don't get many hits, so I'll put this out there in case someone has some insight -

2 years ago I failed the left rear wheel bearing, and it quickly took out the ABS sensor. Both the replacement bearing and sensor were OEM parts.

Last month i was driving in a snow storm and the ABS light came on, which also takes out traction control. Last week I was having the tires rotated at a local chain and asked them to take a look at the ABS issue - they said the left rear sensor was reading intermittently, but they could not easily get the part. I thought it was strange that the 1 new sensor failed again, but I ordered another from FCP and they installed it today, but the problem remains.

I wonder if what looked like a bad sensor was really a bad connection elsewhere in the circuit?

Any thoughts appreciated. I'm already down to front wheel drive, and without the traction control, I'm effectively down to 1 wheel drive.

[AKAMick]

Have you checked the reluctor ring (tone ring) for cracks and excessive corrosion, I had to replace both front rings on my 04 for cracks due to corrosion building up under them, The sensor is only as good as the ring it reads from.

[skibo]

good thought - I had that issue a few years ago and replaced both axles as the rings were not available at that time - they checked and said they were oK - the rear uses a different system where the sensor reads something internal to the bearing - no exposed toothed wheel

[skibo]

Well - Delores went to my neighborhood garage today - they found the same 'staticy' trace on the leff rear ABS sensor (which was just replaced last week) - but they found the surface of the wheel bearing / hub that the sensor 'reads' was somehow corroded (their word - even though I think it's non-metallic). In any case, an hour of labor later they had cleaned up both sides and the problem seems to be solved.

[skibo]

Here is the 'before' trace - after they cleaned up the hub all 4 were the same.

[Astro14]

The sensor works on induction. The reluctor ring MUST be metallic...or there will be no magnetic field...no induction.

It's probably pure iron. That's why it corroded.

[skibo]

Agree - iron or steel - but when I've seen those rear bearings (and I've bought 2 from FCP in the past 18 months) whatever was in there for the sensor to pick up on was hidden from view behind some sort of flat circular non-metallic cover - it's not out in the open like in the front. Maybe the cover comes off or something - I don't know. in 3 months when it warms up I'll get under there to take a look - and (in a perfect world) - maybe clean those up from time to time.