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 1800 (ENGINE CONTROLS AND FUEL - 3.6L - DTC P0008 TO DTC P0193)DTC P0191CIRCUIT/SYSTEM VERIFICATION
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Circuit/System Verification
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Verification
WARNING: This page is about a different car, the 2009 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
- Observe the scan tool DTC information, verify DTC P0627 or P0628 is not set.
- If either of the DTCs are set, refer to DTC P0627, P0628, or P0629 .
- Engine idling, observe the scan tool Actual Fuel Rail Pressure parameter. The pressure should be approximately 3.5-5.5 Mpa (508-798 psi).
- Engine idling, the Actual Fuel Rail 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.
- Move related harnesses/connectors of the FRP sensor and verify the engine does not stumble, stall, or change engine speed.
- If the engine stumbles, stalls, or changes engine speed. Test or repair the suspected harness or connection.
- Observe the DTC information with a scan tool, DTC P0191 should not set.
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. 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.