The fuel injector control module (FICM) 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 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 1 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 in order to operate the CNG injectors. Underhood mounted injector relays are utilized in order 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.
Fuel Mode Operation
The PCM grounds the AF Enable circuit when operating on CNG. When the AF Enable circuit is grounded the FICM will operate the CNG injectors based upon the PCM pulse width signals. The PCM also monitors the FICM status signal circuit for proper FICM operation.
Communication Circuits
FICM Diagnostic Circuit
The PCM monitors the FICM diagnostic circuit in order to set FICM related DTCs. The FICM diagnostic circuit is a 5 volt circuit that is pulse width modulated by the FICM in order to communicate diagnostic information to the PCM.
