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 CARSECTION 114 (BATTERY, CHARGING SYSTEM AND STARTING SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC P0622CIRCUIT/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 car, the 2008 Chevrolet Malibu Classic. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the generator harness X1 connector.
- Ignition ON, connect a test lamp to battery positive voltage and repeatedly probe the generator field duty cycle signal circuit, harness side terminal 2, while monitoring the GEN-F Terminal Signal Parameter in the ECM data list with a scan tool. Verify that the scan tool parameter changes from 0 percent to greater than 95 percent.
- If the GEN-F Terminal Signal scan tool parameter was not affected by the test lamp, then test the generator field duty cycle signal circuit for a short to voltage, a short to ground, a high resistance, or an open circuit. If OK, then replace the ECM.
- If the circuit tests normal, then replace the generator.
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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.