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.
Section 484 (Engine Controls - Self-Diagnostics - 6.0L Bi-Fuel & CNG): Introduction
Sierra and Silverado vehicles are available as a Bi-Fuel vehicle (RPO KL6) or as a CNG only vehicle (RPO KL8). This alternative fuels article applies to both versions. This article should be used in conjunction with the SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article. This article covers only the Bi-Fuel & CNG self-diagnostics. To properly diagnose and repair this vehicle, follow DIAGNOSTIC STARTING POINT - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. If no Diagnostic Trouble Codes (DTC) are present and a no-start condition exists, see BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. If no DTCs are present and a driveability condition exists, see TROUBLE SHOOTING - NO CODES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article for diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).
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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.