1995 Dodge Caravan emissions

21 - Oxygen sensor signal, neither rich or lean detected.
51 - Air/fuel at limit.

Fault codes never say to replaced parts or that they're defective. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. A sensor referenced in a fault code is only the cause of that code about half of the time.

In this case neither code refers to the throttle position sensor. A mechanic would start by using a scanner to view the signal voltage coming from the oxygen sensor. Without a scanner, you can inspect the wiring to the oxygen sensor but beyond that, you'll probably just have to replace it and see if that solves the codes. Throwing parts at a problem isn't the way we like to diagnose things, but sometimes there's no better alternative.

keep doing what you do.cause you have no idea how much it helps for someone who doesn't have an understanding of some areas of auto problems. thanks.