I recently swapped out a used automatic transmission in my 03 Mazda Protege5. My question is I was told that the transmission was good but I do not have any fluid pressure. So I was thinking that the transmission was not good so I put my old transmission back in figured for now I'll just drive with first and second and third and no 4th. However once I put my old transmission back in that doesn't have any fluid pressure now don't understand why. In changing out the transmission do I have to reprogram my PCM? Or what else can be causing the problem I already ruled out the torque converter. Please help