Anti-lock engages, but only when backing down my driveway

[Airman9911]

When I'm backing down my driveway (very slight hill) my anti-lock engages. ABS light does not come on, but the pedal feels and sounds like the anti-lock is activated.

I'm braking just enough to control rolling down hill. Slightly more than the brake lights to illuminate. Once the pedal feels like anti-lock is engaged, I can push slightly harder, it's gone and I stop. Starting rolling backwards again, with very slight pressure, it happens again.

It has happened once when coming to a stop at a red light, again, extremely light brake application. My pads do squeal when applying brakes while taking exits off the interstate or slowing from highway speeds to a stop or a curve. I can let off fully, reapply, and the squealing stops. Could they be very slightly glazed and backing up trips the problem?

 

[Uncle Gump]

I've had similar happen to me... twice.

Both times it was a front wheel speed sensor dropping off at low speed. ABS would sense the brakes being applied and the one speed sensor would stop sending signals... ABS Activated.

Correction was to replace wheel hub unit bearing.

Pretty straight forward to see while monitoring wheel speed data. If you don't have a scan tool... take note of which way the vehicle pulls when the ABS activates. Pulls left... right wheel speed sensor. And vice versa.

 

[Airman9911]

I've had similar happen to me... twice.

Both times it was a front wheel speed sensor dropping off at low speed. ABS would sense the brakes being applied and the one speed sensor would stop sending signals... ABS Activated.

Correction was to replace wheel hub unit bearing.

Pretty straight forward to see while monitoring wheel speed data. If you don't have a scan tool... take note of which way the vehicle pulls when the ABS activates. Pulls left... right wheel speed sensor. And vice versa.

It doesn't pull either way. Just shutters and you can feel the "vibration" in the brake pedal and can hear it chatter.

 

[Uncle Gump]

Then you will need a scan tool that can monitor wheel speed data. Watch them at speeds you have the issue. When it happens I'll bet you see one drop off right when it happens.

 

[Airman9911]

Then you will need a scan tool that can monitor wheel speed data. Watch them at speeds you have the issue. When it happens I'll bet you see one drop off right when it happens.

Wouldn't that throw an ABS light? Because I don't have any light pop up. Just sound and feel.

 

[Uncle Gump]

Mine didn't...

And why would it?

The module simply sees you have brakes applied and one wheel stops. The module just does what it's suppose to do and modulate the brakes to correct it.

Make sense?

 

[pjtoledo]

long shot:

worn suspension bushings allow just enough movement that the wheel slows/stops momentarily with reference to the knuckles/axle.
add weight shift, maybe a slight turn and the ABS is fooled for an instant.

I once had a Taurus that would start ABS every time a specific parking lot entrance was used. it had a significant step.

 

[Airman9911]

long shot:

worn suspension bushings allow just enough movement that the wheel slows/stops momentarily with reference to the knuckles/axle.
add weight shift, maybe a slight turn and the ABS is fooled for an instant.

I once had a Taurus that would start ABS every time a specific parking lot entrance was used. it had a significant step.

Brand new front end. Pa chased cows at 20mph through fields and it was all shot.

 

[Airman9911]

Mine didn't...

And why would it?

The module simply sees you have brakes applied and one wheel stops. The module just does what it's suppose to do and modulate the brakes to correct it.

Make sense?

I can only assume oriellys scan tool doesn't work for ride alongs?

 

[pjtoledo]

Brand new front end. Pa chased cows at 20mph through fields and it was all shot.

ah, screwed up wiring harness's front & rear????
reseat the connectors several times, spray electrical contact cleaner in the connector pins.

2wd or 4wd?

if 2wd check for bent ABS vanes in the back of the front rotor. they pry off and can be manipulated.
if 4wd I'm outta ideas.

 

[Bgunner]

We are talking about the 1993 correct?

In '93 the trucks only had RABS (Rear Anti-lock Braking System) and only one sensor for the system in the rear differential housing.

 

[pjtoledo]

oops

us rust belt guys keep forgetting stuff from the 90's still exists elsewhere.

 

[Uncle Gump]

Geeez...

That sure changes things.

Another good reason to specify what you're working on in your post.

 

[Airman9911]

We are talking about the 1993 correct?

In '93 the trucks only had RABS (Rear Anti-lock Braking System) and only one sensor for the system in the rear differential housing.

It's an 06, sorry

 

[Airman9911]

Geeez...

That sure changes things.

Another good reason to specify what you're working on in your post.

It's an 06, sorry