check engine light

check engine light on in my 98 expy code reads as po171 system to lean(bank 1) just wondering if anyone can help me with this problem and what it might be, an o2 sensor? Thanks

It is a vacuum leak. If you are lucky it is just a vacuum line or connector. More likely it is the upper or lower intake gaskets - these engines have a history of intake gasket leaks.

Yes it was a vacuum leak, Found a cracked hose behind the throttle body. Thanks for the info.