Circuit/System Description
WARNING: This page is about a different car, the 2008 Pontiac G5 and 2008 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
The theft deterrent module (TDM) sends the fuel continue password to the engine control module (ECM) via the serial data circuit. If the fuel continue password received from the TDM equals the password stored in the ECM, the ECM will allow vehicle starting.