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 1803 (ENGINE CONTROLS AND FUEL - 4.4L - DTC P0153 TO DTC P0651)DTC P023ACIRCUIT/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 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the CAC coolant pump relay.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit and ground.
- If the test lamp illuminates, test the control circuit for a short to voltage.
- Verify that a test lamp illuminates between the coil voltage supply circuit and ground.
- If the test lamp does not illuminate, test the B+ coil supply circuit for a short to ground or an open/high resistance.
- Verify that a test lamp illuminates between the B+ switch supply circuit and ground.
- If the test lamp does not illuminate, test the B+ switch supply circuit for an open/high resistance. If the circuit tests normal and the B+ switch supply circuit fuse is open, test the CAC pump voltage supply circuit for a short to ground.
- Disconnect the harness connector at the CAC coolant pump.
- Test for less than 2 ohm between the CAC coolant pump ground circuit terminal 1 and ground.
- If greater than the specified range, repair the ground circuit for an open/high resistance.
- Connect the harness connector at the CAC coolant pump.
- Connect a 10A fused jumper wire between the B+ switch circuit and the CAC coolant pump voltage supply circuit. Verify that CAC coolant pump is activated.
- If the CAC coolant pump does not activate, test the CAC coolant voltage supply circuit for an open/high resistance. If the circuit tests normal, test the CAC coolant pump motor. Refer to Component Testing.
- Connect a test lamp between the B+ coil supply circuit and the CAC relay control circuit.
- Command the CAC coolant pump ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between commanded states.
- If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
- If the test lamp is always OFF, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
- If all circuits test normal, test or replace the CAC coolant pump relay.
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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.