Generally these codes apply to the voltages on power modules.
334 - With main contactor activated, capacitor voltage at power module 2A1 too low.
335 - With main contactor activated, capacitor voltage at power module 1A1 too low.
These are the big, heavy modules on the drive axle. Extremely expensive. The output voltage should be ~ 13V.
Anyway, before panicking,
1. check, and double-check the battery. Check the gravity, voltage reduction while under operation etc.
The electronics on the truck is very sensitive, when teh battery is weak.
2. Check if there's no short circuit from "+" to earth, specially on the thick cables running to the power modules.
3. Double check the red, hot "Oh God!" button. Very often it looks fine, but the contacts are rusted or covered with some sh...t and not conducting properly.
Anyway, I hope, it's one of these lesser issues, because the modules are extremely expensive.
Good luck