I unhooked the passenger side connector at the front of the load cell and showed a LC2 on the scale head.  I got the scale system from Clark’s and installed myself.  I would try swapping wires from the left and right side to see if that gives you a LC3 error.  I think load cell #1 would be the tongue.  If you swap the beam wiring and the error still says LCb2, the problem is in that beam.  Maybe a mouse got to the cable, but you said everything looked ok.  Tom or Nic will help you get things fixed.