Q: I connected an Expression (aka Volume) pedal to my Axiom Pro, but I cannot get it to reach a value of 0 (zero).

A: Some Expression Pedals have a calibration knob that can be used to limit the range of control.  If your expression pedal has this control, set it to the minimum, or so that it allows for the maximum range of control.  If the pedal gets close to zero (e.g 1 or 2), power the Axiom Pro off for 10 seconds and then turn it back on, leaving the Expression Pedal connected.

Note that some Expression pedals, such as the Yamaha FC-7, use a different value resistor and are not compatible with M-Audio keyboards.  In these situations, the values won't even come close to zero (e.g. only down to 20 or 30).