I am throwing a DTC 74 on my 4L80E, Transmission Input Sensor. I searched and was able to find out what this thing does (I think) but the main thing I am trying to figure out is how to fix this.

I just had the transmission rebuilt and the code has been present ever since. I'm thinking one of the connectors on the outside of the tranny might not be plugged in right since my re-builder told me he replaced all the sensors and solenoids.

Does the TIS have anything to do with the connector bank or is that just for the shift solenoids?

Thanks for looking guys!

Nevermind guys. After doing some more research and looking at the code list again I have concluded that the TIS is just the VSS sensor near the bell housing. The same sensor that is in the transfer case for 4x4. Relieved it's a 35 dollar problem to take care of both of them haha

The tiss sensor will create it's own current by the way. Magnetism + motion = voltage. I call it the windmill effect. Vehicle Speed sensors are the same thing.
Glad you found it.

ok guys I am throwing a 74 and 78 codes but seems to come and go. when the ses light comes on have no power! this started with the ses light coming on and if I let off the throttle the light went now when it comes on it stays on tell the key is shut off. however when I go into the pmc it does noy give me the 12 code, was told that the pmc was bad so I bought a used one and it does the same thing no 12 code. so tem me how important is the 12 code? I'm guessing the pmc is going out and the used one I bought is no good as well

The 12 code is telling you that "all systems go" within the computer. it is not a cure all for an answer.
I would check all grounds. Pass through connector going into the transmission. if the pass through connector is wet then replace the O-ring.
Check the ground at the PMC.
Transmission input speed can be checked by disconnecting the tiss and connecting a multimeter with the Alternating current turned on. You should get anywhere between 4.7 volts and upwards to 6 and 7 volts alternating current. The tiss and toss make their own current. Connect the multimeter using the tiny alligater clips found at radio shack. Raise the vehicle off the ground and run through the drive ranges. Use long leads for safety. :)
The Tiss is connect seperately than the pass through connector.
http://i120.photobucket.com/albums/o187/USMILRET/Transconnection.jpg

http://i120.photobucket.com/albums/o187/USMILRET/DTC74.jpg