only somewhat (lower numbers <20) are the same

I would pull the battery out and clean all the corrosion and replace any cables that have been laying in the corrosion as a first step,

for code 48 I have; "Look Ahead" test for A2 volts less
than 12% of battery volts.
POSSIBLE CAUSE
Check for short circuit from the motor armature
to the frame of the vehicle.
Defective control.
*= Replace controller unit.

so if you have a very clean armature to frame you may be going to purchase a not inexpensive controller, but I sure would make sure all the power cables were isolated from the frame electrically..