It's always a good idea to confirm pressing the pedal to the floor causes the throttle to open fully. With the key on / engine off, manually open the throttle fully, at the TB, and check the displayed voltage. If it's significantly different you should check the throttle cable and pedal for obstruction.

If the TB check passes use a DVOM to check voltage across the sensor ground and signal wire. If you find low voltage at WOT further checks are needed. Check signal to engine ground, 5V reference line to engine ground for full 5V, and sensor ground to engine ground for voltage difference. If 5V = 5V, Gnd = Gnd, and signal -> engine gnd = signal -> sensor gnd then you likely have a bad sensor.