Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P1021-P1024: CNG Injector Control Circuit: Description
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.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.