I was curious if you ever figured out what your problem was. I have the exact same thing. Customer replaced the batteries and now has a no crank condition. Starter relay chatters and starter halfway tries to engage. I can jump the starter relay and get it to crank and start up fine. Relay pins have good key on voltage, and good 12 volt signal when moving key to start position. It seems to be a problem with the ground side of ther starter relay, which I'm assuming is controlled by the TCM. Can communicate with the PCM ok and no codes logged, but when I try and receive TCM codes it says no communication. Overdrive light is not working and tranny is stuck in 3rd gear. Have checked all fuses and relays, main hots and grounds and can't find anything. Is the TCM/PCM built into one box on these things? Any help would be appreciated. Thanks!