ABS activating at speed around corners when it shouldn't.

[mparc]

Hi,
Great forum and lots of help for various projects I've tackled. I have a 2004 AWD Aviator 190K miles. (posted it here since it shares components with the same year Explorer).
I have a slight bearing growl coming from the front at very low speeds. It varies with speed and become inaudible over 10 mph. If I shift into neutral while rolling, the sound goes away. The front left wheel ABS has activated 3 separate times when lightly braking on a curve on a mountain road at 45-50mpg and it shouldn't be (quite shocking actually when it happens). I replaced the wheel hubs, no change to the sound (which I suspect is from the front differential now) and the ABS still activates when it shouldn't. The CV Joints have never been changed but the boots are still good and there is no binding or popping. I ve searched this forum and others and can't find anything with these same symptoms. Any ideas?

Thanks!

 

[SoNic67]

If the differential is not right, it might be very well trying to "pull" one wheel more when you are braking, so the ABS will see that and act.
My guess is one of the bearings tend to seize up:

 

[mparc]

Looks like a lot of bearings in the diff. I'm probably looking at full rebuild if that is the problem. Thanks for the info.

 

[corkey]

is the abs light on ?
the growl could be a wheel bearing not a diff bearing,, if the abs light is on, it could an indication there is contamination on the abs sensor from a bad wheel bearing,,

 

[mparc]

Hi,
The ABS light isn't on and I replaced both of the front hubs ( bearings and ABS sensors enclosed) last week. I used Moog components. No change.

 

[1997XLTRollover]

I don't see how a bad diff bearing can cause tire slippage. That bearing would have to be seriously binding up to actually slow the movement of a tire that's in contact with dry pavement.

I've had 2 vehicles do this to me but never at high speed. It was always coming to a stop and I would get an ABS nibble or just hear the pump kick on for a millisecond. In case 1 it was a bad wheel bearing, case 2 it was a bad sensor. Now being that both hubs have been changed in your case, I'm assuming the sensors have also been replaced when the hubs were done?

Assuming that is the case I would think a damaged ABS ring.

Something else I just thought of too, check to be sure rust has not accumulated under a sensor and caused it to pull up off the mounting surface. I would also replace the rear end sensor too. Assuming it's the same as the explorer there should just be one sensor in the diff on the rear. Those sensors are easy to change and don't cost much.

 

[mparc]

Thanks. The hub, sensor and rings are incorporated into one assembly on my vehicle. This is a California car, no corrosion to speak of. I hadn't thought of replacing the rear sensor. Would a bad rear sensor ever cause the front left abs to engage? The vehicle does have dynamic traction control......hmm

 

[SoNic67]

That's the way my hub is - on full assy with the sensor and wiring attached.

 

[gatzdon]

If you have an OBD reader you can connect to your laptop, you can use Forscan to get the extended codes from the ABS module. When the ABS started kicking in on my explorer, the extended codes told me which ABS sensor was failing. Never got the ABS light.

 

[mparc]

I ran the codes last week before I replaced the hubs, all clear. I'm going to try again and also confirm that my reader and software (elm 327 with OBD fusion software) actually pick up ABS codes. Thanks

 

[1997XLTRollover]

Let us know how you make out. I actually have this same sort of issue on my 96 Explorer. No abs light, passenger side hub ring and sensor are new. Drivers hub is tight and I'm getting an ABS pump kick on for a split second at speed every so often. It's happened 3 times in the past few weeks. I have a feeling something is failing again.

 

[gatzdon]

I ran the codes last week before I replaced the hubs, all clear. I'm going to try again and also confirm that my reader and software (elm 327 with OBD fusion software) actually pick up ABS codes. Thanks

OBD software won't pull ABS codes. Forscan is free and does more than just pull OBD codes (it will allow you to push some changes and even initiate some tests).

Forscan Lite on your cell phone is easier to use to pull the codes, but isn't fee (~$5 in the app store).

 

[mparc]

I purchased Forscan and am playing around with it. I haven't yet figured out how to look for ABS error codes. The main "errors" code button lists tire pressure monitor and power control module and they both say "successful DTC reading no error codes found". I'll keep looking and will report back if I find something.

 

[mparc]

Update: I figured out how to read ABS codes from Forscan (great tool by the way, lots of things to explore)......there were no error codes from the ABS module. I'm stumped.

 

[1997XLTRollover]

I just bought a new wheel hub and bearing for the hell of it on my truck. I'm hoping that fixes my issue. Although my abs hasn't activated for a little bit now so who knows why it was kicking on. I'm changing the hub and bearing anyway. With 146k who knows how much time I have left before it fails when I'm in no position to change it. Passenger side went at 144k.

Anyway how about shorted wires? Maybe a harness shorts out when you take a turn and then stops once there's no lateral force on it? Probably a stretch but at this point I have no idea what else could be causing your problem.

 

[mparc]

I'll check the wires closely. Seems like that might have thrown a code though. Thanks.

 

[1997XLTRollover]

It's not going to throw a code if it thinks the tire just slipped. Shorts out and the module just thinks the tire is slipping. Won't have a code in that situation.

 

[gatzdon]

It's not going to throw a code if it thinks the tire just slipped. Shorts out and the module just thinks the tire is slipping. Won't have a code in that situation.

There are codes that will be thrown when the computer concludes that the abs sensor speed differs from the vehicle speed too much. When the ABS is not activated, the speeds should match.

I believe just like many other conditions, the code doesn't appear after one fault, but rather take several faults to activate the code.

 

[1997XLTRollover]

There are codes that will be thrown when the computer concludes that the abs sensor speed differs from the vehicle speed too much. When the ABS is not activated, the speeds should match.

I believe just like many other conditions, the code doesn't appear after one fault, but rather take several faults to activate the code.

While that's possible mine has activated numerous times and has no codes. In his case if the thing is shorting out and it thinks that specific tire is slipping maybe it's screwing something up? It might be a stretch but I'm not sure what else could be wrong.

 

[gatzdon]

While that's possible mine has activated numerous times and has no codes. In his case if the thing is shorting out and it thinks that specific tire is slipping maybe it's screwing something up? It might be a stretch but I'm not sure what else could be wrong.

you will be in new territory for me, but I know the Forscan can read many Ford Proprietary PID values. I wonder if it can read the PID values from the ABS speed sensors (I believe we have three).

If it can read them in real time, you would be able to visually see the speed values and see if one is 'different' from the rest.

Next time I'm driving my 2000 Exp, I'll see if I can find any ABS PID values in the Forscan Lite (can't see the list of PID's in the app unless I'm connected to the vehicle).