CNG fuel injectors
WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
The gaseous fuel injectors are Pulse-Width Modulated (PWM) and sequentially fired. The injector voltage is supplied by the AF relay. The Fuel Injection Control Module (FICM) controls the ground path.