Q: Why can't i fix O2 sensor problem

In many circumstances, the O2 sensors are not the only culprit of a lean fuel curve. In many cases, a clogged fuel injector nozzle can also trigger the most common OBD-II error code (P-2191) that indicates a lean condition exists. Try removing and cleaning your fuel injector nozzles first, then reset your error codes, start the motor again, and complete the scan again. If that doesn’t work, have the previous mechanic check their work or have another local expert, like one from YourMechanic, diagnose the Check Engine code to have it properly corrected.