Very occasionally the ABS will activate at less than 10 mph at normal braking. I've scanned for codes and found none. ABS bulb does work on startup and goes out and never comes on during this issue. Ive searched and people say one of the sensors or tone rings is bad. How do you tell if a sensor is bad? Id hate to throw money at the problem and replace everything ***** nilly. I haven't noticed any correlation to if im turning or not. generally its a straight stop it does it.

 

You'd have to look at the signal and see if it consistent.

You might check the grounding of the sensor and ECU. Give them some fresh metal to contact.

 

alright ill have to setup my scantool to observe this. Would you know where the sensors ground and ECU ground? Truck is a 2001 ranger edge 3.0 5 speed reg cab reg bed 2wd so Ive been cleaning grounds as I find them. Craptastic factory star washer grounds are just that.

I know the previous owner replaced both calipers rotors and wheel bearings.

 

Alright drove to work this AM with scantool attached. at very slow speeds (less than 3mph) the right front would drop to zero then come back while left front would read whatever (ex: 1.84mph) nice and steady. Scantool doesnt update but once a second and no graphing available for those specs... My guess is the right front sensor is the wonky one as a few seconds its reading the same as the left but then it drops off to zero.

Another goofy thing I saw is while at 30 mph the rear sensor was slower than the fronts by 2mph, at 65 mph it was off by 3-4 and 75 it was off by 4-5mph... What would cause the fronts to read different than the rear? The fronts above 10mph matched each other (within 1mph) All tires are the same size and brand and roughly the same tread thickness and same air pressure. Is that normal? 2wd truck mind you.

 

Tested with scan tool again still right front sensor behaving flaky at less than 5. Got the bolt out easy as could be for the sensor but its rusted up in its hole...I assume I have to remove wheel, caliper, wheel bearings, rotor to get to the SOB to take a punch and whack it out? 2wd mind you as its perpendicular to the wheel, not like the videos Ive seen on 4wd its facing the axle.

 

Got old sensor punched out, checekd the tone ring on the rotor - looked good no damage and flat. is a patch of rust but the windows are still great. Got new sensor put in and its behaving exactly like the old one was. Speeds less than 5 mph the right front will intermitantly go way low or zero then come back while the other 2 stay steady.

I cleaned the 2 grounds by the fuse box and that made it run smoother bu tno change on abs issue. Where does the sensor ground at? Any known grounds that get crusty rusty? I will have to follow the wiring back i belive and see where it goes...

 

didnt follow wires back. I heard you can use an ohm meter or AC volt meter and connect it to the sensor wires then spin the wheel as constant as you can and it should produce steady numbers. Mine occasionally on VAC dip to zero and ohms would not change. I took the sensor back out of the spindle to see if i could see the tone ring wobble - i cant see any wobbling. When i had the rotor off for sensor replacement it was not cracked or damaged or bent. There was a small patch of rust on it but still very solid. Would a rusty spot cause issues? Is it possible to move the sensor closer? farther?(guess i could slip a washer under the holddown bolt)

.. Sensor is new and behaving exactly like the old one so the only part thats the same is the dang rotor thats only 2 years old or spindle somehow.

 

I spoke with a shop about this issue and he said the new sensor could be bad (unlikely) but he has seen where the rotor tone ring has the incrorrect number of slots which can freak out the module. Has anyone ran across this?