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 642 (POWER STEERING SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC C056DCIRCUIT/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 2010 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the X2 harness connector at the PSCM.
- Ignition OFF, test for less than 5 ohms between the ground circuit terminal 1 and ground.
- If greater than specified value, test the ground circuit for an open/high resistance.
- Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 6 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, reconnect the X2 harness connector. Disconnect the X3 harness connector at the PSCM.
- Ignition OFF, test for less than 5 ohms between the ground circuit terminal 3 and ground.
- If greater than specified value, test the ground circuit for an open/high resistance.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 1 and ground.
- If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
- Test for B+ on the control circuit terminal 10.
- I less than specified value, test the control circuit for an short to ground or an open/high resistance.
- Ignition OFF, reconnect the X3 harness connector. Disconnect the X1 harness connector at the PSCM.
- Test for less than 5 ohms between the signal circuit terminal 7 and the signal circuit terminal 8.
- If greater than specified value, test both signal circuits for an open/high resistance. If the circuits test normal, test or replace the upper intermediate steering shaft.
- Test for less than 5 ohms between the signal circuit terminal 7 and the signal circuit terminal 14.
- If greater than specified value, test both signal circuits for an open/high resistance. If the circuits test normal, test or replace the upper intermediate steering shaft.
- Test for less than 5 ohms between the signal circuit terminal 8 and the signal circuit terminal 14.
- If greater than specified value, test both signal circuits for an open/high resistance. If the circuits test normal, test or replace the upper intermediate steering shaft.
- If all circuits test normal, replace the PSCM. If the DTC resets, replace the upper intermediate steering shaft.
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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.