Circuit Description
WARNING: This page is about a different car, the 2003 GMC Savana and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) grounds the Alternative Fuel (AF) enable circuit when operating on CNG. When the AF enable circuit is grounded the Fuel Injector Control Module (FICM) operates the CNG injectors based upon the PCM fuel injector control pulse width signals. On Bi-Fuel (KL6) vehicles the PCM opens the AF enable circuit when gasoline operation is desired. Switch-over from one fuel to the other is always performed in an orderly, sequential manner. Since some injectors are in the middle of injecting the previous fuel, the FICM will wait until that cylinders fuel delivery is complete and will then switch over in sequential firing order.