ABS-Weird Problem - Help

I have a an International with Bendix ABS.  Under the cab on the inside frame rail, next to the transmission,  I have a Bendix ABS computer.
This computer has a series of lights on it that tell me what's wrong with it when it's not working right. In the past, when the ABS light on the dash turned on, I would crawl underneath the truck and look at the lights.  It
usually said something like, "frt, left, sensr, vlt."  So I replace the front left sensor, reset the computer using a magnet and swiping it past the computer per the reset directions.  All codes would clear and everything was great.

I got an ABS light on a few weeks ago.  Computer tells me it's the right rear sensor.  I replaced both rear sensors since I was doing wheel seal anyway.  (there are only sensors on the rear axle btw). Cleared the codes and everything was happy for a while.

Soon after, when turning on the truck, I got an ABS light again.  The truck didn't' even roll.  I cleared the codes and it was fine for a few start ups and then it did it again.

When I turn the key on before starting, the ABS light momentarily turns on as it goes through it's self-check where you can hear it cycle the ABS solenoids at the different axles.  When it's done, the ABS light turns off. I start the truck and usually after about 5-10 seconds, the ABS light turns back on.  I check the code and it says "rht, rear, sensor" again.  Remember that the truck hasn't even moved.

I can reset the computer and drive it forever with the ABS working good (I tried it) and no light.  I checked and cleaned all the plugs and connectors from the computer back to the wheel sensors.  I drove it about 200 miles this weekend after resetting the light and it never came back on.  When I got home, I parked it.  I started it the next day and the same thing happened.  Only this time after about 3 minutes, it turned off on it's own.  I have not checked to see if the computer still has lights on but the dash light is off.  I cycled it a few more times and it's fine so far.

So, any ideas?  Could the sensor still be bad and it's throwing code during the self check? and why wouldn't it throw a code when driving if it is out of range?  Should I try another sensor?  What are the chance of two bad
sensors?  Could it be the tone ring?  Do they go bad?  Wheel bearings are tight and adjusted with no play btw (not that it should matter if the truck isn't moving)

First thing I would ask, does your truck have an ABS blink code switch?  Or a driver's display of some kind?  I recommend either of those, you could get more specific fault codes either by counting the blinks or reading the code on the driver's display.  You can check the sensors at the connector using an ohmmeter. should be around 1800 ohms +/- say 300 ohms for a good sensor. short or open circuit = bad sensor (or bad test - It's hard to get the ohmmeter leads down into to that connector).  While you're plugged up you can rotate the wheel and look for a voltage albeit it's as black and white as I make it sound.

Need to also chase all the wiring back to the ECU.

Could be wheel bearing end play as well, if the hub moves away from the sensor the signal drops off fast.  Especially if you just changed wheel seals, it's hard to get the hub to the required values, usually 0.01 to 0.04
inches but check International's recommendations to be sure.  Need to use a dial indicator, and do it without the drum on.  Your hands aren't calibrated, too loose, ABS faults, seal damage, too tight, risk of damage to
bearings.  Could also just be that little clip around the sensor, they work really well until they stop working then they don't work at all (there's an intelligent statement LOL)

Gotta stay off the computer when I come home for lunch.

I'll stick an ohmmeter on the sensors and see if they fall within range or at least if they are the same.  Will also check for voltage at the same time.

Wiring seemed good all the way to the computer.  I cleaned all the connections.  I had it running with my wife watching the light while I went underneath and pulled and tugged on all the connectors and the entire harness hoping to find an "intermittent open."  Still nothing.

I didn't change the wheel seal on the that wheel.  I also didn't put on a dial indicator on it either.  It did seem tight when I grabbed it and pried on it though.  Of course I come from a car/small truck background where you can feel a loose hub.  Maybe you can't on these HDT's?  So I'll re-torque the wheel bearing and then dial indicator it and make certain I'm within range.

Little clip thingy is brand new with the new sensor.

Should I replace the tone ring while I'm in there?  Do they go bad?  There are no chips or any visible damage to it.

Also, if it was something like wheel bearing being too loose, or bad sensor, why would it not throw a code when I was rolling/driving? and why would it do it when it's just sitting still? That's the part that has me stumped.

In the main wire harness it is really hard to see a frayed wire that gives a resistance change.  Also check to make sure the sensor bracket is clean & makes a good ground.  Some need to be really clean as to not change the
resistance.  I have chased wires with a basic light tester & found a bad spot in the wire with no visible signs to the out side of the insulation but when striped back it had just the smallest fray but it did cause problems.  I had troubles with a trailer & finally put some die electric grease in the coupling & that must have helped the resistance enough to stop the troubles.  They have very small wires inside & I tried to solder a wire & had more trouble & ended up replacing instead.  Electrical problems can be very hard to find sometimes & it can drive you nuts until you find it.
Good Luck,
Gordon

I doubled checked and cleaned the holder for the sensor.  Cleaned the tone ring real good.  Reset the hub preload/end play to manufactures specs.  Re-cleaned the plug connection and squirted some dielectric grease on the all the connections.  Checked resistance and found it to be approximately 1720 also picked up a constant voltage while rotating the hub.  Light still comes on.

It's weird though.  You can start it and drive it miles with no problems. It's only right after you start it.  Sometimes.  I turn the key on, it cycles with the light on as it should, then it goes out.  Then I start it and a few seconds later (maybe 10) it turns on.  Lately it has been turning itself off after about a minute.  There are no codes on the computer either.  Mind you I haven't even moved the truck or even touched anything.  Sometimes the light will stay on until you clear it.

I left it running and went after all the wiring pulling moving and tugging on it trying to find a problem or loose connection with no luck.  Just for giggles I unplugged the sensor while running.  It instantly threw a light and it wouldn't turn off even when I plugged it back in I was thinking maybe a ground?  I don't know where it grounds but tried all the ones I could find.  I also pulled the box off the frame and cleaned the box to frame connection which was really dirty and corroded.  I don't think the
box relies on a ground though.  I would assume it has it's own "wire" ground.

Sooo? any other ideas?  I'm getting ready to pull the light out of the dash. haha

Guess I don't have any hot tips, but I feel your pain!