The hood release mechanism in a Honda Civic is located behind the vehicle's front grille. A hood release cable runs from this mechanism to the hood release lever inside the vehicle. When this cable breaks, you can't open the bonnet using the bonnet release lever. The hood release mechanism contains a small release lever that is accessible through the vehicle's front grille. This lever is normally actuated by the cable, but you can also actuate it manually.
Shift the Civic's transmission into first gear (manual) or park (automatic) and turn off the engine. Apply the parking brake.
Locate the hood latch release lever on the hood latch mechanism. It is on the right side of the hood latch mechanism. It is visible by looking through the vehicle's front grille, just above the Honda emblem. The hood release cable attaches to the far right side of the hood release lever.
Insert a flathead screwdriver into the grille and pry the hood latch release lever to the right until the hood releases.
The hood latch release lever can be pretty stiff, requiring a fair amount of prying pressure to release the hood.