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.
Circuit Description
Fuel Indicator Light (FIL) informs driver what fuel engine is operating on. This vehicle utilizes a Powertrain Control Module (PCM) and an Alternative Fuels Engine Control Module (AF ECM) in order to control engine operation. AF ECM controls CNG engine operation and PCM controls gasoline engine operation. AF ECM and PCM are connected by AFO Signal circuit. AF ECM will command CNG engine operation by grounding AFO Signal circuit. PCM will turn OFF FIL whenever AFO Signal circuit is grounded. Instrument panel gauge fuse supplies positive voltage source for FIL. PCM supplies ground path.
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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.