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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 10 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 4.3L - DTC P0016 TO DTC P0336)DTC P0131, P0132, P0137, OR P0138CIRCUIT/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 variant/trim than selected.
    IMPORTANT: All modules must be powered down or misdiagnosis may result.
  1. Ignition OFF, disconnect the scan tool and wait 60 seconds to ensure all modules are powered down.
  2. Ignition OFF, disconnect the harness connector at the appropriate HO2S.
  3. Ignition OFF, measure for less than 5 ohms between the appropriate HO2S low signal circuit terminal A and ground.
    • If more than the specified range, test the appropriate HO2S low signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Ignition ON, verify the appropriate scan tool HO2S parameter is approximately 450 mV.
    • If more than the specified value, test the appropriate HO2S high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    • If less than the specified value, test the appropriate HO2S high signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
  5. Ignition ON, install a 3A fused jumper wire at the HO2S high signal circuit terminal B. Toggle the jumper wire between the HO2S low signal circuit terminal A and battery voltage. Verify the appropriate scan tool HO2S parameter toggles between 0 mV and approximately 1,000 mV.
    • If the appropriate scan tool HO2S parameter does not toggle correctly, test the HO2S high signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.
  6. If all circuits test normal, replace the appropriate HO2S.
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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.