I suspect your truck has a ge sx controller. code 16 is battery volts too high, this can be adjusted with the lx handset - function 15.

is it possible it had a 36volt battery and now has 48?

I can send you my sx manual if you have an e-mail address.

also some forklifts with this controller require specific settings for function 15 that only the oem manual can tell you or someone who knows the truck.