po 174 bank 2 system lean

my truck says it is running to lean isnt my computer in the truck supposed to keep that from happening?

It tries to keep the air/fuel mixture at an ideal level; however, things like a vacuum leak, clogged injector, low fuel pressure, bad 02 sensor, etc can cause a lean condition that the computer can not correct for so it sets the check engine light.

//2000CAYukon

i swapped the o2 sensor and about 1/2 a year ago put in a fuel pump . the light turned on twice so far about once every 2 weeks i was just hopping for the magic fix