I have a 2000 ranger with the 4.0 and 4x4, when i come to a stop on dry pavement the abs will kick on. I have hooked it up to a snap on modis scanner to see which speed sensor is acting up but right before the abs kicks on the modis loses comunication with the vehicle. there are no abs codes in memory and the abs light never comes on. any ideas?

 

Welcome to FTE.

If your Not having any problems with the speed-o, cruise control, or tranny shfting, as they too use input from the rear differential ABS speed sensor, you can probably eliminate the rear speed sensor from your suspect list.

SO, that would leave us looking at the two front speed sensors & seeing as how you don't have a set code, maybe get down there & have a look at the sensor & the wheel tone ring, for rust scale, or other debris on the ring or sensor, or maybe a wiring problem, or internal sensor heat sensitive electrcal problem.

If no joy, maybe disconnect the sensors electrical connector & look for moisture, corrosion, bent or broken pin or spread socket, ect

If still no joy, seeing as how the problem seems to be related to heat, maybe try heating the sensor with a hair dryer, or heat gun & see if it's resistance chagnes, or opens up with heat.

OR, maybe it isn't an ABS problem, but something like a warped rotor, contamination on the disc or pads, thats causing uneven friction.

Did the problem come about suddenly, after some event????

On the scantool loosing communication with the vehicle, does it seem to be related to vibration, deceleration, brakes coming on, loose fit in the DLC connector ect????

Some thoughts for consideation, let us know what you find.

 

Gentelmen! this is not so rare problem on early ATE ABS. It is no so sufisticated and no air gap, bearing play and damaged tone ring test. If air gap is more then 0.2 mm tone voltage on low speeds is too low and ABS unit consider this wheel locked and try to kick with pump and valves to unlock wheel.

first of all check for bearing play ajust bearings if necessary. then to check all you need a AVOM (not DVOM becouse of delay). what wheel sensor do you sugest to get this issue?

ATE is the German company and according ECE regulations vehicle must not turn in direction of opposidte of wheel that skids and that's why ABS unit applies both the front brake valves but drops more pressure on locked wheel. so it is not so easy to understand what wheel sensor generates lower voltage.

now, turn ignition off. jack up the weel, unlplug ABS Sensor connector and measure resistanse. Usually it is 1.2K, but depending on brand may vary from 900 to 1900 ohm.

Then check bearing for play. and select ~0-5V range on AVOM. Turn wheel at appr. 3-5 MPH. Usually voltage is about 1.2-2V. If lower, ABS unit reads lower 5MPH speed and if speed changes from 15 mph to lower speed too agressively ABS program consider this weel locked.

yeah, sometimes abs sensor core iw worn with dust, sand.... air gap is more then must be.

well, now you know what start with...

 

Good information input Pablo UA.

 

Did you work on the front brakes recently? I'll bet the ABS unit needs to be bled..

 

the problem we discuss now are usual for old ABS systems. Newer systems have tone ring rattle, air gap, tire size (important for trucks with ASR) and wheel skid tests. When truck runs over 5 mph, no brake applied system checks and compare wheel speeds, for diagnostic purpuses new systems measure not only frequancy (wheel speed), but the voltage too.

But we have prev. generation ABS systems so I have to check for this with AVOM....