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 12 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 6.6L (LMM) - DTC P0300 TO DTC P0699)DTC P0506 OR P0507CIRCUIT/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.
- Verify that DTCs are not set. If DTCs are set refer to Diagnostic Trouble Code (DTC) List - Vehicle
.
- If DTCs are set refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- Engine running, compare the scan tool Desired Idle Speed parameter to the Engine Speed parameter. Both engine speed parameters should be within 50 RPM of each other.
- Elevate the engine speed in 25 RPM increments to 1,300 RPM using a scan tool. With each commanded increment, the actual Engine Speed parameter should stay within 25 RPM of the commanded speed.
- Operate the vehicle within the Conditions for Running the DTC to verify that 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.