Running lean

Have you changed the fuel filter? When was the last fuel injector service? If light still comes on after that is done, run a fuel pressure test, pressure might be low.

You may have a intake or vacuum leak somewhere. Make sure the intake is snugged up and check the throttle body base gasket, & all vacuum lines. This is more info on the code....P0171 CHEVROLET - Fuel Trim System Lean Bank 1... Possible causes... - Intake air leaks - Faulty front heated oxygen sensor - Ignition misfiring - Faulty fuel injectors - Exhaust gas leaks - Incorrect fuel pressure - Lack of fuel - Faulty Mass Air Flow (MAF) sensor - Incorrect Positive Crankcase Ventilation (PCV) hose connection... Some Tech notes... If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replaced the air filter and clean the air flow meter. If the problem persist the front oxygen (O2) sensor may need to be replaced. The P0171 code could also be caused may be caused by one or more of the following: debris on MAF sensor causing an incorrect reading, improper oil level, low or high fuel pressure or Engine Control Temperature (ECT) Sensor reading inaccurate.... There is a service bulletin on this you may want to look up...http://goo.gl/ZOB29 - or - 2000-2008 Chevrolet Factory Service Bulletin OBDII Code P0171