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 1893 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 4.3L - DTC P0016 TO DTC P0336)DTC P0068 OR P0121CIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Circuit/System Testing
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2009 GMC Savana and 2009 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
- Inspect for the following conditions:
- Vacuum hoses for splits, kinks, and proper connections as shown on Vehicle Emission Control Information label
- Inspect thoroughly for any type of leak or restriction
- Air leaks at throttle body mounting area and intake manifold sealing surfaces
- Throttle body for dirt, debris, and coking-Refer to Throttle Body Cleaning .
- Allow the engine to reach operating temperature. Observe the MAP Sensor Voltage parameter with a scan tool. Voltage should be more than 0.8 volt and less than 4 volts.
- If more than 4 volts or less than 0.8 volt, refer to DTC P0106 .
- Idle the engine. Observe the MAP Sensor kPa parameter with a scan tool. Increase the engine speed slowly and then back to idle. The MAP sensor kPa should change smoothly and gradually as engine speed is increased and returned to idle.
- If the MAP sensor kPa does not change, refer to DTC P0106 .
- Take a snapshot of the engine data list while performing the actions listed below. The mass air flow (MAF) sensor g/s should change smoothly and gradually as the engine speed is increased and is returned to idle.
- Idle the engine.
- Increase the engine speed slowly to 3,000 RPM, then back to idle.
- Exit from the snapshot and review the data.
- Observe the Mass Air Flow (MAF) Sensor parameter frame by frame with a scan tool. The MAF sensor g/s should change smoothly and gradually as the engine speed is increased and is returned to idle.
- If the MAF sensor g/s does not change smoothly and gradually as the engine speed is increased and is returned to idle, refer to DTC P0101 or P1101 .
- Inspect the throttle body for the following conditions:
- Loose or damaged throttle blade
- Broken throttle shaft
- Any throttle body damage
- If any of these conditions exist, replace the throttle body assembly.
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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.