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 1659 (POWER TAKE-OFF SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC P0641CIRCUIT/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 Sierra, 2009 GMC Cab & Chassis Sierra, and 2009 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF. Disconnect the harness connector at the PTO switch.
- Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 1 and ground.
- If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PTO module.
- If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the PTO module.
- Clear all DTCs. Verify that P0641 sets as current in the PTO module.
- If the specified code does not set as current, test or replace the PTO switch.
- Ignition OFF, connect the harness connector at the PTO switch.
- Disconnect the harness connector at X124.
- Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal E at the female side of the connector and ground.
- If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PTO module.
- If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the PTO module.
- Ignition ON, test for 0 volts between the 5-volt reference circuit terminal E at the male side of the connector and ground.
- If greater than the specified value, test the 5-volt reference circuit between X124 and the upfitted remote PTO switch assembly for a short to voltage. If the circuit tests normal, test or replace the upfitted remote PTO switch assembly.
- Ignition OFF, test for infinite resistance between the 5-volt reference circuit terminal E at the male side of the connector and ground.
- If less than the specified value, test the 5-volt reference circuit for a short to ground. If the circuit tests normal, test or replace the upfitted remote PTO switch assembly.
- If all circuits test normal, replace the PTO module.
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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.