Trailer ABS problems
 

Had a brake job early December a few weeks after that the ABS light came on. Seems extremely intermittent. Getting a code (3 flashes) for passenger side ABS sensor. I tested the sensor while the code was active and the resistance was normal. I noticed it was a ways from the exciter ring so I pushed it back onto it. The code went away immediately.

However I went to wash the trailer (not even a mile away) and as I came back the light came on again. I'm thinking during the brake job - which included wheel seals - they maybe messed up setting up a bearing?

The senser or senser's could have dirt or grease on it, or there could also be dirt and grease in the rotor teeth, if there is dirt and grease there, resetting will not fix the problem, only cleaning the senser's and rotors. And if that won't work, popping the light bulb will.

If it was due to the seal replacement the fault would have showed up right away, unless the axle nuts have backed off over time. It might be worth checking them.

Is this a Wabco system? Did you test the sensor by unplugging it from the ECU and getting your reading from there? Some have extension cables so you have to make sure you test that part of it also. 1000-2500ohms or so is a good reading. If you see the beginning of any corrosion on the pins that's enough to cause intermittent problems. Of course it's a moot point if the 3 flash code is an air gap code. I'll see if I have the codes at work tomorrow.

Yes it's the meritor wabco system, code is for sensor YU1 I believe, which is the passenger side. The resistance was around 1300 ohms, same as the other side. The pins are not corroded, and I put a nice glob of dielectric grease in there.

I'll try cleaning the teeth off. Thanks for the tips.

Jack up the wheel end. Remove both wheels, brake drum and hubcap. Measure wheel end-play with a dial indicator. It should not exceed 0.005". Mine are always less than 0.003"... which the TMC adjustment method will NOT give you without a re-adjust. I would not be surprised if you find this spec way off.

P.s. - your wheel seals and bearings will live much longer with less than 3 thou end-play as well.