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.
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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 108 (ENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L BI-FUEL)DIAGNOSTIC TESTSDTC P1204: VEHICLE DOES NOT OPERATE IN CNG MODETEST DESCRIPTION
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Test Description
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Test 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 numbers below refer to the step numbers in the diagnostic procedure.
- 4 - This step determines if a CNG specific DTC is causing the condition. If one of the listed DTCs is set, diagnose that DTC first.
- 5 - This step determines if the engine will start and idle.
- 7 - This step determines if the CNG fuel system is the cause of the concern.
- 8 - This step determines if the ignition system is the cause of the concern.
- 9 - This step tests the injector monitor circuit to the FICM. An open injector monitor circuit will set this DTC.
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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.