P0172 Fuel Trim Code in 2011 Chevrolet Impala - Rich Running and Hard Starting Issues
I own a 2011 Chevrolet Impala and am currently experiencing a P0172 diagnostic trouble code. The vehicle is difficult to start in the morning, and when it does start, it runs very rich initially. After driving for some time, the condition improves and the car runs normally for the rest of the day. I took it to a repair shop, which confirmed that fuel pressure is within specifications and remains stable during engine-off conditions. However, I'm still experiencing inconsistent performance. Can anyone provide insight into potential causes or troubleshooting steps for this P0172 code? Any advice on what to check next would be greatly appreciated.
P0172 is a rich fuel trim code — ideally, we should review live data such as Fuel Temperature (FT), Engine Coolant Temperature (ECT), and Throttle Position Sensor (TPS). You mentioned that fuel pressure was checked and holds under KOEO (Key On, Engine Off) conditions. However, testing fuel pressure with the engine off does not fully assess injector performance or fuel delivery issues. It's important to verify if there is a pressure drop when the engine is running. Additionally, take advantage of free diagnostic scans at auto parts stores — don't assume that no warning light means no code. Common factors to investigate include using an oiled air filter or an incorrect thermostat.