Finally figured this one out. Brake Coil was bad.
Also check for "stray" frequency! I just had one that exhibited the same symptoms. Turns out the coils were being saturated by frequency emitted from the drive motor. It would never acquire the wire and the drive unit would hunt back and forth while trying to align. Unfortunately, the drive motor had to be replaced.
Thanks Popeye & PESLLC, I will check these things. It is an older SP, so I was wondering about stray voltage.
Have you tried to raise the sensor to see of the scales change. This may help determine if the issue is even sensor related. I have also had a goofy truck that no matter what we did the sensor read saturated. I ended up making an extension to the bracket to raise it about.5" above the max. It has been running fine for over a year now.
Check for voltage to frame before and after engaging traction you might find a bad drive motor or Access #3 putting voltage to frame and the sensors are picking it up. Might be brake coil also, but I have not seen that since old SP days.
Thanks Popeye, that was a good idea. Interesting, when off the wire, I am getting 00,00,01,00 on both GS1 & GS2; however, as soon as I engage the traction (move traction handle either PUF or FF) both sensors go to something near 80,99,99,80 (in other words-saturated).
So tonight I am going to try Ifixit's idea and try swapping out modules 5 & 6 to see if either changes behavior, as well as look for loose or frayed wire that may be causing the input voltage.
If anyone has ideas on where to look for voltage appearing to be sensor pickup when off wire, tips are appreciated.
On the sensor bar between the load wheels is it the correct one for your floor power. Crown has both low and high gain depending on power from wire in floor. You can eyeball truck centered up on the wire then go in through the display and look at GS1 and GS2 inputs to see what the sensors are seeing. You will see 4 sets of 2 digit numbers. 2 middle sets are the ones on each side of wire and other 2 are the outside sensors.
On the bright side, you have a lot of donor trucks to swap parts with to see if the problem stays or moves to the other truck
Thanks Ifixit, I have checked for all the usual mechanical reasons; but the source seems to be the "saturated coil" message. The SP thinks it is "on the wire" even when it is not. We have 50 SP in the same area and this is the only one exhibiting this issue; so I doubt it is the transmitter (floor wire). I have changed out both sensor bars and am not receiving any fault/event codes associated with WGU except the 636.
I'm taking a guess, here. Have you checked the steer bearing? Sits above the drive unit. I've seen them start to go bad and physically steer the truck off line.