DTC P1021-P1024: CNG Injector Control Circuit: Description

WARNING: This page is about a different car, the 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

The Powertrain Control Module (PCM) controls fuel delivery and determines fuel system operation on Bi-fuel (KL6) vehicles. The PCM is not capable of operating the high current CNG fuel injectors. When CNG operation is commanded, the PCM grounds the AF enable circuit, which energizes the AF relay. The AF relay energizes all of the AF injector relays. The PCM injector control signals are routed through the AF injector relays to the Fuel Injector Control Module (FICM). The FICM generates duplicate control signals to operate the CNG injectors. Ignition voltage is supplied to the fuel injectors. The FICM controls each CNG fuel injector by grounding the control circuit via a solid state device called a driver. The FICM monitors the status of each driver. If the PCM detects an incorrect voltage for the commanded state of the driver, a fuel injector control DTC P1021-P1024 will set. DTC P1021 will set if there is a condition on a CNG fuel injector control circuit for cylinder 1, P1022 for cylinder 2, etc.