Need help-"Check engine light?"

I'm new to this board. I was wondering if someone had any suggestions as to what might be causing my "check engine light" to remain on. I bought an OBD II diagnostic tester and I got a "PO171" reading, which was a "fuel system lean" indication. I then changed the oxygen sensors (both upstream and downstream) on my 1997 Ranger (2.3L, 4 cyl., 5 sp.) and erased the code, however, the "check engine light" keeps coming back on. Does anyone have any other ideas as to what may be causing the check engine light to be activated? Thanks.

it would still have the same code? fuel system lean?

i dunno why u changed a part that didn't need it... i know there's a code for the o2 sensors. < P0130-P0141>

back to topic- running lean: when's the last time you have changed your fuel filter? that's a start... to rule out a fuel restriction. then u gotta hook up a fuel pressure gauge and/or check injectors for clogs (doesn't it has a code for injectors?--i guess not)

then check for vaccuum line leaks... mebbe around the egr area is putting too much burnt gasses back into the intake & leaning out the mixture... isn't there a code for that too? < P0400/ P0402>

having an excessive lean sytem is no good--increased temps so keep an eye on the temp gauge if u have one. (temps won't be increased in the egr dumping too much exhaust back to the intake, though)

NE ways, clear the codes, drive around again, see if engine light goes on yet again, read codes...

Thanks for the advice RiceBike. I'll check for vacuum leaks and change the fuel filter.