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.
SYS.OK|MANUAL.DBβ LIVE
HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 2159 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 4.8L, 5.3L, 6.0L, 6.2L - DTC P1255 TO DTC P3449)DTC P2270 OR P2272CIRCUIT/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 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
All modules must be powered down or misdiagnosis may result.
- Ignition OFF, disconnect the harness connector at the appropriate B52 HO2S.
- Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes, test for less than 5 Ξ© between the low reference circuit terminal A and ground.
- If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
- Ignition ON, verify the appropriate scan tool B52 HO2S parameter is approximately 450 mV.
- If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
- If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- Ignition ON, install a 3 A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool HO2S parameter is less than 60 mV.
- If greater than the specified range, test the signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.
- Verify none of the following conditions exist:
- Lean fuel injectors-Refer to Fuel Injector Diagnosis (CH47976) or Fuel Injector Diagnosis (J39021 or Scan Tool)
- Water intrusion in the B52 HO2S harness connector
- Low fuel system pressure-Refer to Fuel System Diagnosis (Without FPCM) or Fuel System Diagnosis (FPCM)
- Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool)
- Exhaust leaks near the B52 HO2S
- Engine vacuum leaks
- Contaminated B52 HO2S - Silicon
- An engine mechanical condition- Symptoms - Engine Mechanical
- If you find any of the above conditions, repair as necessary.
- If all circuits test normal, replace the appropriate B52 HO2S.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.