I've taken the car on numerous "drive cycles" and the oxygen sensor remains "not ready." The repair shop wants to replace all oxygen sensors, I cannot afford this and it seems unnecessary. Is there anything else I can do? Is there a drive cycle specifically for a not ready oxygen sensor? (not heat sensor BTW)

How do I correct or diagnose

Is it common for the rear brake pads to wear out after only 23.5k miles? No warning of impending damage to rotor via scrapper tabs...none notice on pads. Comparative front to rear pad surfaces, I still have approx. 80% lining left on fronts. Also noted significant pad size difference with the rears being much smaller pads. Possible design flaw given this vehicle is rear wheel drive with traction control? Or possible problem with electronic parking brake allowing rear brakes to drag. Anyone with input on this matter?