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 410 (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 2009 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
- Verify that a test lamp illuminates between the generator output B+ circuit terminal B X2 and ground.
- If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
- Ignition OFF, disconnect the harness connector X1 at the generator.
- Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter displays less than 5 percent.
- If greater than the specified range, test the signal circuit terminal 2 X1 for a short to voltage. If the circuit tests normal, replace the ECM.
- Install a 3A fused jumper wire between B+ and the signal circuit.
- Verify the scan tool ECM GEN-F Terminal Signal parameter displays greater than 95 percent.
- If less than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
- If the circuit tests normal 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.