bank 1 running too lean, is that a blown gasket, bad O2 sensor or a clogged injector?

Question

2002 GMC Seirra threw a po171 code bank1 running too lean. where should I start first, o2 sensor, blown gasket, or clogged injector?

Answer 1

P0171 Fuel system lean Bank 1

First is make a visual inspection look and listen for any vacuum leaks that are unmeter , and this includes the intake gasket when a engine runs lean ,air entering the engine that gets past the MAF (Mass airflow) is unmetered this throws out the fuel to air ratio. If this was a clogged fuel injector you can expect a Random misfire code and a cylinder misfire code with a lean code.  If this was a blown headgasket you can also expect a random misfire with a rough idle.