Have a SC4020-30 that began to lose power while traveling. The BDI would flicker and display multiple codes finally displaying a solid code-68. Service manual suggested troubleshooting code -66 first before moving on to code -68 troubleshot motors for shorts, load tested battery - all check good. Determined master is bad, replaced and programed. During power up code -17 (Brake mod) displayed. Replaced part and calibrated. This where I chased the rabbit down the hole. Long story short every time I replace a component the unit will throw another random code during power up. Due to heavy corrosion from battery, Replaced upper controller wire harness and distribution board to help eliminate the communication codes (every time I moved or unplugged / connect the wire harness a communication fault code between controllers would be displayed) So now after replacing all these components, Unit is powering up, showing no codes, but now has no travel. Verified master and slave programmed correctly also calibrated all pots multiple times. History of items replaced:
-Master
-Slave
-Brake pot mod
-Distribution board
-Wire harness (top control)
-Battery (swapped with known good)

Strange thing is when you turn the wheels all the way to the right and dead head it, the drive motors will turn both directions. But when you start turn (even an inch) to the left, nothing. Units steer and hydro functions all work correctly. Also, unit has no height switch option (sorry meant to say tilt inter lock function). Has anyone experienced this? Any help appreciated. Any one has any idea why this is happening or have experience this problem.