P0171 : System too lean bank 1
P0174: System too lean bank 2
These codes let you know the O2 sensors are creating a lean condition. Since it is apparent on both sides of the engine we can rule out a blown head gasket or injector issue. We can even rule out a misfire. The majority of the time this is caused by a vacuum leak. There are several hoses that can become weak and collapse. Pay close attention to all the vacuum hoses. These codes may be accompanied by a rough idle. Replace the hoses as needed. On some vehicles you may even find the intake gasket leaking(plastic intakes).