The code tells you which sensor is bad. If the wiring harness to the sensor has not been chewed on by a rodent I'd start with the sensor replacement. You may need to have the code erased with a scan tool. When an electrical sensor for the transmission goes bad it puts the vehicle in fail safe mode and you only have 3rd and reverse gears. If no other codes get set you don't need the other sensors. If the light on the dash says TCM that's for the traction control...NOT the transmission control module! In that case you probably have a bad wheel speed sensor. If the transmission is shifting properly it's not a transmission problem.

if check engine light on for speed sensors all you have to do is replace the sensors then have the light turned off by disconnecting battery cables from the battery for several minutes. no need to rebuild the transmission or replace the tcm unless there is a problem with either one

Cars suck. Ride a bike.

You don't need to replace the transmission. Change only what is necessary, and enjoy your vehicle.

Will I have to replace this if the light doesnt go off after I replace the output sensor on a 2003 automatic dodge neon and do I have to replace the input speed sensor also and if I'm replacing all these sensor is it best to just replace tranny oh 116,000mikes on it and its been sitting up awhile if that makes a difference