I have a 97 Ranger with 4.0 Litre V-6. The check engine light recently came on. I did a diagnostic test at a local parts store and the codes displayed showed it needed both of the front bank O2 sensors. I had replaced them last July so they were under warranty so I replaced them again. Everything was fine for a few days then I got the check engine light on again. Did test again, same thing. Codes show O2 sensors reading lean. Assuming it may not be the sensors that are bad, what are the other components to check? I already checked vac lines. They are fine. Electrical connectors for sensors also look good.

 

Possible dirty MAF sensor telling the computer that less air than there really is causing the computer to inject less fuel causing a lean condition.