DTC B2796: No Communication In Engine Immobilizer System: DTC Detecting Condition
WARNING: This page is about a different car, the 2002 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
DTC B2796 is output when an ignition key has been inserted into ignition lock cylinder that does not contain a transponder chip, or when communication between ignition key and Engine Control Module (ECM) is impossible.