My Bighorn (4JG2 A/T) has a switch near the Transmission Selector Lever that toggles between "Power" and "Normal" with corresponding indicator light in the dash. I understand it suppose to alter the shifting points but I can hardly feel the difference. Any ideas how to test if this is still functioning?

I am beginning to suspect that it is somehow stuck in the "Power" mode because it downshifts with just a little pressure in the loud pedal (also very sensitive)