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 2159 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 4.8L, 5.3L, 6.0L, 6.2L - DTC P1255 TO DTC P3449)DTC P2271 OR P2273CIRCUIT/SYSTEM VERIFICATION
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Circuit/System Verification
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Verification
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.
- Ignition ON, observe the DTC information with a scan tool. Verify that no B52 HO2S heater DTCs are set.
- If any B52 HO2S heater DTCs are set, perform those diagnostics first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- Engine idling, move the appropriate B52 HO2S 2 harness connector and the engine control module (ECM) harness connector while monitoring the B52 HO2S 2 voltage parameter with a scan tool. Verify that the B52 HO2S parameter does not change abruptly while moving the related harnesses.
- If the B52 HO2S parameter does change abruptly while moving the related harnesses repair the circuit as necessary.
- Engine idling at operating temperature, observe the appropriate B52 HO2S 2 parameter with a scan tool. Verify the following:
- The B52 HO2S 1 value should vary from below 200 mV to above 800 mV and respond to fueling changes.
- The B52 HO2S 2 should fluctuate at less than 380 mV or greater than 520 mV. The values should not remain within 380 mV and 520 mV.
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
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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.