What model and year?
How have you determined it is reading in reverse?
Software or multimeter?
If multimeter then the black probe of the multimeter needs to be on the negative supply to the throttle position sensor (TPS) and the red probe on the "wiper"
If you are reading reverse, then I expect you are measuring between the positive to the TPS and the "wiper"
That is the only way you would measure the opposite of what the ECU is sensing.