you may want to try it this way

1. Start with the key switch OFF.
2. Remove the logics cover.
3. Place the DIAG/RUN/SETUP switch to DIAG.
4. Turn the key switch ON while pulling back on the
LIFT and TILT levers.
The fault codes will appear on the display, beginning
with the most recent.
To toggle through to the next code move the DRS switch back to run and then back to diag and it will cycle to the next code stored, when you reach the end of the list the display will indicate 'done'.
I would also check and see what operator mode the truck is set in... it could be set to a slower mode causing the slower performance.

But before you do any of this always check the battery condition and make sure it's not just a dead battery ;o)