ABS activates while stopping

[gorp00]

1997 XLT. When coming to a slow stop the ABS comes on just before the vehicle come to a full stop. No ABS light and it does not happen under hard braking, just slow, easy stops. No codes and ABS/traction unit passes tests but pedal is a little soft.

Could it be failing wheel sensor(s)?

 

[SWIGIN]

My daughters 97 did this too and shortly after that started she had a major hard line failure.

 

[poker4me007]

I'd say it's one of the front wheel sensors.I had one do the same thing and the abs light never came on.If you can get your hands on a abs code reader you can probably see what wheel is giving you the problem.

 

[donalds]

I'd say it's one of the front wheel sensors.I had one do the same thing and the abs light never came on.If you can get your hands on a abs code reader you can probably see what wheel is giving you the problem.

You have a good video on replacement on your YouTube


Here is how I solved my brakes pulsing under 5 mph

Solved P0500 c1102 pulsing breaks under 5mph

 

[J_C]

On my '98, the left front sensor was causing this, and replacing it (off brands are much cheaper on amazon than anything Rock Auto has), worked fine for a few months, then it started happening again because that hub was slowly failing.

Note that new hubs usually come with the ABS speed sensor (if the front for a 4WD or AWD) so you might want to first try cleaning the sensor off, and checking the hub for any play but there may be none detected yet, mine seemed fine at the time. Point is, if there's a chance the hub is going out, you might just want to buy the hub w/sensor instead of wasting money on a sensor like I did then having to buy a hub anyway that includes one. My hub was original and at a little over 100K mi so it was due for replacement.

You can try removing the sensor and cleaning it off, but mine broke attempting to remove it from the hub. Mine is 4WD so it's in the hub rather than external with a ring on the back. The end of the video below shows the external type but the whole video is useful.

You can use forscan app with an ELM327 code reader dongle to see the sensor values, which sensor is dropping out as you replicate the problem coming to a stop. I've been writing about the front but could be either side, or the single rear sensor on the differential. Briefly it is :

0. Disable Sleep mode/screensaver in your laptop, if necessary.
1. Connect FORScan to vehicle, go to Dashboard (or Table, or Graphs) section
2. Change module to ABS
3. Double click on any gauge, the PID profile dialog will open. Select the PIDs you need and move them to the right side of dialog. Close the dialog with OK button
4. Press Start button
5. Make the trip. Please note that managing laptop while driving is not safe, so please ask somebody to assist, otherwise be very careful.
6. Click Save button to save the data you collected to FSL or CSV format.

If you're not going to get this fixed right away (need to use the vehicle), you can pull the fuse for the ABS module to stop ABS from activating at all. Depends on the situation if it's worse to not have ABS working at higher speeds (suppose a !@#$ deer runs out in front of you), versus having it misfire while you're coming to a stop behind someone at a stop light or sign.

 

[Pete Deering]

1997 XLT. When coming to a slow stop the ABS comes on just before the vehicle come to a full stop. No ABS light and it does not happen under hard braking, just slow, easy stops. No codes and ABS/traction unit passes tests but pedal is a little soft.

Could it be failing wheel sensor(s)?

No, I replaced my sensors, huds and lube slides and replaced calipers and brake pads. It happens from time to time.

 

[J_C]

^ That is not proof that it couldn't be failing wheel sensor(s). It usually is a lack of signal from one, then the question is whether it is the hub wearing out, contaminated sensor, broken sensor, broken sensor pigtail wire, bad electrical connection to the harness wire, damaged harness wire.

ABS activating feels quite different than other mechanical brake problems, and can be ruled out by pulling the fuse to the abs module. If it continues without power to the abs module, it can't be abs activating.

 

[Pete Deering]

^ That is not proof that it couldn't be failing wheel sensor(s). It usually is a lack of signal from one, then the question is whether it is the hub wearing out, contaminated sensor, broken sensor, broken sensor pigtail wire, bad electrical connection to the harness wire, damaged harness wire.

ABS activating feels quite different than other mechanical brake problems, and can be ruled out by pulling the fuse to the abs module. If it continues without power to the abs module, it can't be abs activating.

I replaced both front hubs and sensors ( sensors comes with hub).

 

[Pete Deering]

I also replaced the rotors too.

 

[Pete Deering]

Both front sensors are new, everything in front is new. Still a little pulse. not is bad as before.

^ That is not proof that it couldn't be failing wheel sensor(s). It usually is a lack of signal from one, then the question is whether it is the hub wearing out, contaminated sensor, broken sensor, broken sensor pigtail wire, bad electrical connection to the harness wire, damaged harness wire.

ABS activating feels quite different than other mechanical brake problems, and can be ruled out by pulling the fuse to the abs module. If it continues without power to the abs module, it can't be abs activating.

 

[J_C]

^ Hook up a scan tool capable of looking at wheel speed sensor values while the event happens, or unplug the abs fuse as mentioned previously.

There is also a 3rd abs sensor on the rear differential. If the two sensors in front are working properly that could easily be it.

However your case is strange in that until you replace the faulty part, the problem should remain about the same, not diminish unless you had multiple sensors bad which would be quite a coincidence to happen simultaneously unless one had gone bad and you lived with it until yet another failed.

I would pull the abs fuse. If the pulse is still there, it's not abs related.