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:
| • | internally routes the powertrain control module (PCM) injector control circuits to the CNG injector drivers or the gasoline injectors (KL6 only) |
| • | operates the CNG injectors based upon the PCM injector signals |
| • | supplies the reference, ground and signal circuits to the fuel rail pressure (FRP) and fuel rail temperature (FRT) sensors |
| • | communicates the FRP sensor values to the PCM using a dedicated PWM circuit |
| • | communicates the FRT sensor values to the PCM using a dedicated PWM circuit |
| • | communicates FICM, FRP and FRT diagnostic information to the PCM using a dedicated PWM circuit |
The PCM controls fuel delivery and determines fuel system operation on Bi-fuel (KL6) equipped vehicles. 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 3 PWM communication circuits 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. KL6 equipped vehicles utilize a FICM that contains internal relays. When operating on gasoline the internal relays allow the PCM injector pulse width to go directly to the gasoline injectors.
Fuel Mode Operation (KL6 and KL8)
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 FICM will convert the FRP and FRT sensors voltage signals to independent PWM signals that the PCM monitors for fuel trim adjustment. The PCM also monitors the FICM Diagnostic Input circuit for proper FICM operation.
KL6 Operation
When gasoline operation is desired the PCM opens the AF Enable circuit. Switchover 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.
Communication Circuits
FRP and FRT Sensor PWM Circuits
The fuel rail pressure and temperature sensor information is required by the PCM for fuel trim adjustment. The PCM does not have the ability to supply and monitor the FRP and FRT sensors. The FICM performs this task by supplying the FRP and FRT sensors a 5 volt reference, low reference and signal circuit. The signal voltage of the FRP and FRT sensors are converted into independent PWM signals. The PWM signals are sent to the PCM through dedicated circuits. The PCM converts the PWM signals into pressure and temperature values. The FICM also performs diagnosis of the FRP and FRT circuits as well as internal FICM diagnostic information. The FICM diagnostic information is converted into a PWM signal. The FICM PWM signal is sent to the PCM through a dedicated circuit.
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. The FICM Diagnostic Data table indicates the various PWM signals created.
Diagnostic Data | PWM Duty Cycle |
|---|---|
gasoline operation | 25 % |
CNG operation | 50 % |
no input activity for more than 5 seconds | 56.25 % |
FRT high voltage | 62.5 % |
FRT low voltage | 68.75 % |
FRP high voltage | 75 % |
FRP low voltage | 81.25 % |
CNG injector fault | 87.5 % |
FICM internal fault | 93.75 % |
