given the wide range of systems JLG has used in their lifts over the years one thing that would help immensely is the unit's serial number so we can get your answers more quickly.
at this point we are just guessing at it...
but like the previous poster said, the fault codes are generally 2 digits.
The fault light will flash one number then pause and flash the other number, then pause longer and then repeat it.
If you can get your hands on a JLG handset that will show you what it is as soon as you plug in and turn the unit on, it defaults to showing faults at startup if there are any present.