The code 2 is a normal status before travelling. The code 8 should be flickering, but should not come on when you first move the control handle out of neutral. The code 8, flickering means that the truck is trying to go into high speed. The code 5 is the status for normal travel. The code C is for when the system senses too high a voltage at the #1SCR. I would check the potentiometer in the handle first after checking the battery. Then I would check the drive motors and the heat-sink for the #1SCR and the #1SCR. You said that when you push the contactor in manually the truck takes off at high speed, that is not normal. It usually means that the #1SCR is shorted or that the "M" speed contactor is welded shut. Hope that this helps!