ABS intermittent activation on dry pavement

[Frankd1]

I noticed recently that my abs will activate slightly when coming to a stop...it is intermittent and on dry pavement...

Would this be an indication of a faulty sensor? Could I remove the sensors and clean the mounting point?

I replaced the front wheel hub assemblies on both sides and they are relatively new, I used Timken hubs..

2003 Envoy SLE

 

[kickass audio]

if it activates at 5mph or less on dry pavement then it could be a dirty sensor or a faulty hub in the front despite being recently replaced. I tried to take my sensors out and clean them but ended up snapping them off in the hub so I would never try to get the sensors out personally again.

 

[Sparky]

New hubs would be easy to get the sensors out of though.

One could be defective. Should be under a warranty.

 

[Frankd1]

Yeah it happens right around 5 or 6mph...

When you say a faulty hub, do you mean a bad sensor or the hub itself?
I can't detect any play or noise in the hub bearing, which if there was, I'm guessing would cause the abs sensor to not sit properly while stopping at slow speed with wheels turned....causing abs to activate..

I'll pull them and clean them and check resistance and voltage at the connector..
Is this how you determine if they are faulty?

Thanks

 

[Mooseman]

95% of the time this happens, it's a faulty hub no matter if the sensor is replaced or the hub is noisy or loose. The other 5% is the sensor.

I once had it with brand new hubs but they were cheap Chinese crap. I heard from an ex-gm tech that sometimes it's caused by rust under the sensor that pulls the sensor away from the reluctor.

 

[Sparky]

When my hub was going bad, it had no visible play nor made noise (at first) but ABS would randomly trigger at low speeds. Later on the hub started to growl, then howl, but still had no visible play.

 

[Frankd1]

Ok thanks guys. I'll dig into it and see what I find...

Just out of curiosity, what occurs if the hub is bad that causes the abs sensor to trigger? if there is no rust otherwise underneath the sensor pulling it away

 

[Mooseman]

Not entirely sure but my guess would be looseness in the thousandths of an inch causing it. Not enough to be heard or felt but enough to cause problems.

 

[gmac310]

I had this on one of my hubs and when I removed the sensor the reluctor was filled with grease. No way of getting that out from between the teeth so I had to buy another one.

 

[Frankd1]

Haven't had a chance to get to this yet as I'm on the road travelling. ABS is still chirping away at slow speed.

Out of curiosity I pulled the ABS fuse today - #33 under the hood, the yellow abs light illuminated but so did the red brake warning light.

Is the red warning light supposed to come on as well?

I don't feel entirely comfortable driving with the red warning light so I'm going to put the fuse back in.
I thought by pulling the #33 fuse only the abs light would come on....

I'll have a chance to pull the wheels and check the hubs and sensors early next week. But until then....

 

[Mooseman]

The brake light coming on is normal. I would rather drive with ABS disabled than get low speed activation.

 

[Frankd1]

Thanks Mooseman.

I thought for sure only the yellow abs light would come on with pulling the fuse. So needless to say, I was a bit surprised to see the red warning light as well.
You are right though, having abs constantly activating at slow speed is a pain and dangerous too.

Are there any issues with ruining the system by driving with it disabled?

 

[Sparky]

Nah. 99% of the time the system just sits there anyway.

 

[Frankd1]

Awesome, thanks!

 

[Frankd1]

Has anyone come across 5 sided Allen type keys?
That's what's holding my abs speed sensor to the hub....some kind of security fastener.

Why timken couldn't use a standard Allen fastener bolt is beyond me.

Any suggestions?

 

[Mooseman]

Vice-grips?

 

[Tiggerr]

Force a torx in there....