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 DIAGNOSISELECTRICALGAUGESINSTRUMENT PANEL SYSTEM DISPLAYS & GAGESDIAGNOSTIC INFORMATION AND PROCEDURESDTC P0523CIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G3500, Van Passenger Extended
Circuit/System Testing
2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the EOP sensor.
- Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit terminal 1 and ground.
- If greater than 1 ohm, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
- Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 2 and ground.
- If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the ECM.
- If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- Install a 3-amp fused jumper wire between the signal circuit terminal 3 and the low reference circuit terminal 1. Verify the scan tool Engine Oil Pressure Sensor parameter display is less than 8 kPa (1.2 psi).
- If greater than 8 kPa (1.2 psi), test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
- If all circuits test normal, test or replace the EOP sensor.
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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.