Fuel Injector Control Module: Notes

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 Fuel Injector Control Module (FICM), located on the left side of the radiator support behind the fascia, is a non-flashable control module that is not capable of serial data communication. The FICM performs the following tasks:

Operates the CNG injectors based upon the PCM injector signals.
Communicates FICM diagnostic information to the PCM using a dedicated PWM circuit.

The Powertrain Control Module (PCM) controls fuel delivery and determines fuel system operation. The PCM monitors various engine and vehicle functions to provide the correct amount of CNG or gasoline fuel under all operating conditions. The fuel injector control circuits, an AF Enable circuit and PWM communication circuit connect the PCM to the FICM. The PCM is not capable of operating the high current CNG fuel injectors. The PCM injector pulse width signals are received by the FICM and duplicate pulse width signals are generated by the FICM to operate the CNG injectors. Underhood mounted injector relays are utilized to switch the injector signal between the FICM and the gasoline fuel injectors. When operating on gasoline the injector relays are not energized, allowing the PCM injector pulse width signal to go directly to the gasoline injectors.