Sounds like your brake caliper or brake line/hose is causing the issue. If it is returning slowly (relaxed position), it will show erratic signal...because it is differing in wheel speed from the other wheels. If the sensor was showing more revolutions, it would think nothing of this...since it would think you are just spinning the wheel. But, when it sees slower wheel revolutions during take-off...it considers it erratic (not constant with what type of data it should be recording). Example, all other wheels are at 100 revolutions per mile and one is 96 rpm (because its showing a slight amount of drag)...brake module doesn't understand such a reading on take-off and figures something is wrong with that wheel/brake. And sets a code. If your code has disappeared, I'd assume it's the caliper...since you may have taken it "past" its bad spot. However, I'd change them both if it reappears.

Brian.

 

Thanks, Brian. Interesting analysis; makes sense. If it recurs I'll note what the circumstances are, but I recall that when the dreaded chimes sounded the last time a week and a half ago I was sitting at a stoplight.

 

Brian, as I think more about your analysis, if the caliper and pad are returning/relaxing more slowly than the other three would the wheel actually be turning more slowly than the others, triggering the fault, or would the pads and disc on that wheel simply show more wear due to the pads dragging a bit? No difference in wear was evident on the pads or rotor of this wheel vs. the other.

Also, what about the line and/or hose would cause the restriction? There is no visible evidence of any damage to the hose or the steel line (where visible, of course). As I was trying to compress the piston I thought momentarily that something back at the modulator might be causing the problem but I don't (yet) understand the operation of the ABS modulator to know what that might be.

 

The inside of the rubber hose deteriorates and causes a obstruction inside, fluid can be forced through one way with the assistance of the foot pressure and power brakes...but...the return process is hampered by the obstruction. The only thing reentering the pads away from the rotor is the natural run-out of the rotor.

Maybe, there wasn't much difference in wear...because it just started hanging up? Time will tell.

​​​​​​​ Brian.

 

Again, thanks for the explanation, Brian. I'm glad I noted in my post that the right piston was more difficult to compress than the left piston. In keeping with the "When unsure, replace less expensive parts and complete easier repairs before the more expensive, more difficult," I'll install a new caliper and a new hose if the Boys from South of the Border return.

 

When I bought my truck it was in desperate need of new pads and the amigos showed up upon hard application of the brakes on the test drive, but disappeared with a key cycle. Then on the ride home after purchasing it they were on full time. Fresh pads corrected the amigos problem but I also had a piston which gave me trouble compressing and this caliper hung and chewed through a set of pads in about 50 miles, accompanied by excessive heat and a ton of dust (obviously). I bought a replacement caliper and another set of pads from NAPA and I've had 4k trouble-free miles since. Over the last few days however the amigos have been showing up intermittently but a key cycle always clears them. My kitbest OBDII dongle doesn't appear to address ABS issues as no codes ever show up however twice when I have started the truck the ABS light does not extinguish and a split second later the other two amigos join it for the full amigos compliment. I will go through and check the sensor connections but suspect I may be buying replacement sensors soon.

 

I don't know for certain whether or not the caliper or the hose is the cause of the RR WSS intermittent erratic signal fault, but regardless of that there's clearly a problem with one of the two so I'll be doing some more diagnosis. The RAVE says "Clamp brake hose to prevent fluid loss." Just how is that done, given the hose is wrapped with a steel coil to protect the hose and prevent it from kinking (I presume)?

 

 

Well duh, plugging the line instead of clamping it makes a lot more sense. In almost 9 years on this forum that may be the most embarrassing question I've asked!

 

I’m planning to remove the RR caliper today to test it, and see whether or not the piston moves smoothly in the bore off the truck. If so, that will point to the problem being in the hose and I’ll replace the hose. If not, I’ll replace the caliper. Stay tuned.