THE C5 uses a new-generation coded engine immobiliser with a code-transmitting transponder that is linked to the engine computer. Doors and boot are locked and opened by a three-button remote control unit that operates without needing to be pointed directly at the receiver. If the vehicle is accidentally unlocked, it locks again automatically after 30 seconds if none of the doors has been opened. The boot locks automatically once the vehicle is under way. A perimeter and volumetric alarm is fitted, but only the V6 gets a deadlock system.