1991 ford 150 302 auto diagnostic code 63 tp circuit below min voltage where and what is tp circuit?

tp = throttle position. assuming all else is working properly, i.e. ground, power supply, and signal, this means the throttle position sensor output is too low. you have to adjust the throttle position sensor (assuming it is adjustable) to reach the minimum desired by the ecm.

I think that means Throttle Position circuit,,,,,as in throttle position sensor.