Steer card only gives code G4. Not the problem
Before doing anything, check radial ring wear. If worn, steer motor amps go up. GD code
if brushes are worn on steer motor, GD code. If toothed ring slips on drive unit, GD code
If steer prox is not even at full CC. CW turns, GD code, Stee prox adj clearence is.020 thou. Check it. If it's hitting the steel rail, Radial rings are shot
If steer motor spline slips, GD encoder fails, GD
If dog **** on right rear load wheel, GD code.
Good luck...let me know what you find...or...do like most people on this site, never respond and leave us hanging!