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 G3500, VAN PASSENGER EXTENDEDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 10 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 6.6L (LMM) - DTC P0016 TO DTC P0299)DTC P0191CIRCUIT/SYSTEM VERIFICATION
2008 Chevrolet Chevy Express G3500, Van Passenger Extended
Circuit/System Verification
2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Verification
WARNING: This page is about a different variant/trim than selected.
IMPORTANT:
- You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
- If you cannot duplicate the condition, operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
- Verify that DTCs P0652 or P0653 are not set.
- If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- Observe the Fuel Rail Pressure Sensor parameter with a scan tool. During engine cranking, the pressure should be at least 10 MPa. With the engine running at idle, the pressure should be close to the Desired Fuel Rail Pressure. As the engine speed increases, the Desired Fuel Rail Pressure and the Actual Fuel Rail Pressure should closely match each other.
- Engine running, observe the DTC information with a scan tool. DTC P0191 should not set.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
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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.