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 P0652 OR P0653CIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G3500, Van Passenger Extended
Circuit/System Testing
2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Testing
WARNING: This page is about a different variant/trim than selected.
- Turn OFF the ignition for 30 seconds or until the ECM powers down.
- Disconnect the accelerator pedal position (APP) sensor.
- Turn ON the ignition, with engine OFF and measure the voltage from the 5-volt reference circuit of the APP sensor 2 to a good ground with a DMM.
- If the voltage measures 4.7-5.2 volts, replace the APP sensor.
- With the DMM still connected to the 5-volt reference circuit, disconnect all other components connected to the 5-volt reference 2, one at a time. Refer to Diagnostic Fault Information .
- If voltage changes when one of the above components is disconnected, replace the component. Refer to the appropriate replacement procedure.
- Test the 5-volt reference 2 circuits for a short to ground or a short to voltage.
- If no problem was found in the 5-volt reference 2 circuit, replace the ECM.
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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.