printout require replacement of PCM?

Question

Chevy Silverado LS 5.3L LS diagnostic printout reads U0100 noticed excessive gas usage

Answer 1

U0100 Loss communication with ECM (engine control module)

For this code condition you would need to check for "P" codes. and "B" codes, P0100 doe not mean you have faulty ECM or TCM it  just mean it  did not make the communication. this can be low battery voltage, or a module that is not communicating.