before you try to replace the controller you may want to verify the performance mode setting.
If you are familiar with how to change performance modes try to do this first when you start up the machine. Change it to a different mode.
Generally when you are changing modes the horn will sound off telling you what performance mode it is in 1 beep is mode 1, 2 beeps is mode 2, and 3 beeps is mode 3.

If you need assistance on how to do this proceedure here it is:
step 1- control handle in upright position
step2 - press horn button while turning on the keyswitch, release the horn button when the horn sounds.
step 3- toggle through the mode selection using the lift or lower buttons, the horn provides an audible indication as to what mode it is in as i mentioned above.
step 4- lower the handle to the operating position, the mode will stay until it is changed.
DO not turn off the key before lowering the handle, doing this will cancel the mode change.

try this and let us know what happens.