Circuit Description

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The powertrain control module (PCM) enables the appropriate CNG fuel injector on the intake stroke for each cylinder. The PCM is not capable of operating the high current CNG fuel injectors. The PCM injector pulse width signals are received by the fuel injector control module (FICM) and duplicate pulse width signals are generated by the FICM in order to operate the CNG injectors. The FICM controls each fuel injector by grounding the control circuit via a solid state device called a driver. A fuel injector coil winding resistance that is too high, or low, will affect engine driveability. A fuel injector control circuit DTC may not set, but a misfire may be apparent. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings will increase as the temperature of the fuel injector increases.