2006 GMC Suburban P0175 and P0172 Error: Diagnosis and Solutions
I'm experiencing OBD2 fault codes P0175 and P0172 on my 2006 GMC Suburban. Both codes indicate a rich air-fuel mixture on bank 2, which could point to issues with fuel delivery or sensor readings. I'm looking for guidance on where to start troubleshooting—any recommendations? I've checked the fuel filter and spark plugs, but the problem persists. Can anyone confirm if this is related to fuel composition or vacuum system components?
If your 2006 Suburban is equipped with a 5.3L flex-fuel engine (E85 compatible), using regular gasoline instead of E85 may trigger these codes. In such cases, a fuel composition reset via a reliable OBD2 scan tool is often required to correct the air-fuel ratio settings. A Technical Service Bulletin (TSB) exists for this issue. Additionally, inspect the vacuum assist fuel pressure regulator—remove the vacuum line while the engine is running and check if fuel flows from the regulator. A ruptured or leaking regulator can cause a rich condition on both engine banks.