Chevrolet Repair: service engine soon light on 99 Z71 V8 5.3 L, oxygen sensors, o2 sensors

Question
My service engine light is on and I can't get it inspected.  Apparently the code is reading "too lean" on 1 & 2.  I had my fuel filter and pump replaced recently and my light is still coming on. I was told that it was probably not the oxygen sensors.  Any ideas? (I apologize for lack of information on the resulting codes)

Answer
Hi katie....well it could be a couple of things....a too lean cond, can be caused by faulty inj. or plugged inj. O2 sensor could be reading wrong on that bank...you will need to install a scan tool and take O2 readings from that bank, it should be bank 1 sensor 1 and bank 1 sensor 2... which sensor is telling you that you have a lean problem....the one before the converter or after...if it's the one before (bank1 sensor1) then i would look at plugged or faulty inj...if it's the downstream (bank1 sensor2) i would look at the sensor...when was the last time you had O2 sensors replaced...they should be done about every 50 to 60 thousand KLMS or approx 40 thousand miles. Take sensors out and look at the ends...they should be a light gray...if they are black or oil covered they should be replaced...also if you are using fuel that has ethnol it can also affect the sensors as well...hope this helps...merry christmas