software version 8.4 and newar added code 83 - travel control handle pot out of neutral

well knowing a little bit about the ray/cat trucks they are very similar to the raymonds, when they show a code 83 it is an E-Stop error.
Without knowing for sure what system is in your truck i'm just throwing this out here, it may or may not help.

Runtime FMEA has detected that the E Stop button was down.

System response-
-Alarm sounds: yes
-Operators Display:'Lift Emergency off button' turn key OFF
-PC contactor: denergised
-VM Display: 83
-Brake activated: no

Problem in the estop circuit

Possible causes:
estop switch defective
carriage board defective
mast cable bad
VM bad

this information may or may not help

Are you sure its code 83? The book shows code 81, then skips to 84, there is no 82 or 83.