ABS Light

[Todd Robida]

I've been having the following issues with my brakes on my 2001 Explorer ST.



At first, when I slowed to a stop on dry pavement, my ABS would activate momentarily and then the ABS light would come on. Now, my ABS light is on all the time. ABS has not activated on dry pavement recently.



Based on ideas found in this forum, I tried the following:



1. Check brake fluid level.

2. Bled the front brake calipers. (I have rear drum brakes. No ABS on rears, I assume)

3. Checked for frayed wires at firewall / parking brake mechanism area.

4. Checked ABS sensor connector forward of wheel house.

5. Removed rotors and cleaned sensors and surrounding area.



Does anyone have any other ideas? I'd prefer to solve this without getting a mechanic involved.



Thanks,



TRR

 

[Larry C]

I would also have someone scan you OBD-2 for codes. Autozones if there's one near you does it for free. There maybe more info there. The newer OBD-2 systems have codes stored even if teh CEL is not on. then have them clear teh coded.



You can also try some of those brake shops, car-x and see if they do free inspections.



Good luck.

 

[shawn stonbraker 2]

Do you still have the original rotors or have you changed them? If not the only other thing it could be is a bad sensor.

 

[Todd Robida]

I changed the rotors about 2 years ago. Both were flaking with rust.



Is there some sort of flag in the rotor that the sensors sense? If so, neither rotor seemed to have anything on them.

 

[shawn stonbraker 2]

Vehicles used to. I don't think the ST does though. I would still say it's probably a bad sensor. Since everything you listed earlier are cures for the more common problems.

 

[Hal S]

TRR,

can't tell from your profile if you have a 2 or 4 WD.

Excessive front wheel bearing play (most common in a 2 WD), could cause your problem.

Some sort of a scan tool that could monitor PIDs would find it real quick, but the most likely cause is a wheel speed sensor air gap or failing sensor.

For what it's worth, as long as the ABS light is illuminated there will be no ABS activation as the system disables itself when it turns on the warning indicator.

 

[Todd Robida]

Thanks for all the replies.



Does anyone know how to test a sensor? What resistance should be measured across one? When turning the wheel, there should be an AC signal coming from the sensor, I presume?



I have 4WD. I have no excessive front wheel bearing play.



Speed sensor air gap? Is that the distance from the sensor to the rotor? Maybe rusting is causing the gap to get larger. (material falling off and ID of rotor getting bigger).



Looks like 2 possible culprits. Bad sensor (which one?) or Bad rotor (which one?)



TRR

 

[Kevin Palmer]

If you can get somewhere that can plug in and read LIVE DATA you will get you answer. With a live data reader it will display the actually reading the ABS Module is seeing. Pretty easy to isolate the issue out from there as you will clearly see a difference by comparison to the other sensors.



And you do have rear ABS. It is internal of the third member. If you look, you will see the sensor mounted onto the top of the punkin.