System for retaining a motor vehicle bonnet

The system has a hood locking/unlocking case (3) with a housing (10) arranged on an inner face at a part emerging from a wedge lock. A restraint axle (12) of a hood is locked in the housing under an effect of a piston (5). An ordinance device having a magnetic suction cup (14) stops pushing of the lock by the piston. A detection unit activates the device when it detects an effective or imminent impact against the vehicle.