So, all brake pads have plenty of wear left on them as they were replaced 17k miles ago. I have R&Red both brake pad wear sensors (one is brand new replaced by me today) and they appear to be in perfect condition and not worn through which I know they do when the pads become thin enough. But the message "brake wear...visit workshop" message remains. What to do?

 

The brake wear system activates when one of the wires shorts to ground OR goes open circuit. Your next step is to check for shorts or opens on all wires which are part of those circuits.

 

check rear right side sensor harness. you most likely pinched it ... very common

 

I may have pinched the front right when I R&R ed the right front axle because the message began appearing after that job. I have carefully checked the wiring harness but have found no apparent damage or kink. Should I replace the harness from the sensor plug to and behind the inner "fender flap" or what?"

 

Unplug the sensor wire to the brake pads at the right front. Jury rig a short wire to bridge the plug contacts in the body part of the connector -ie make the system think there is continuity and no ground fault from that part of the brakes. No need to put the wheel back on. If the problem is in the brake pad portion the fault will clear. If that doesn't work, carefully check the body wires for pinched/broken faults.