Hi, Alan it should be noted O2 sensor failure is very often misdiagnosed due to other underlying issues. One of the jobs of your onboard computer (ECM) is to regulate the timing and the amount of air and fuel being delivered into the combustion chamber for maximum burn and efficiency, it does this by collecting and processing data from all the sensors in the electrical system. If this data is outside parameters due to faulty sensors or wiring it will generate a fault code and try its best to compensate for a condition that may not even exist, it is "IMPERATIVE" that you only have a trained, skilled, and experienced professional to do a proper diagnosis of your issue, repair the problem right the first time to prevent wasted time, "MONEY" and comebacks. That being said the usual suspects are:
1. Age like spark plugs they wear out you should replace every 100K.
2. Faulty wiring causing the sensor to give corrupt data to ECM.
3. Intake or exhaust system leak causing corrupt data to ECM.
4. A cheap quality aftermarket brand sensor you should use Bosch OEM.
5. Contamination from cheap poor quality or leaded fuel.
6. Contamination from excessive engine "blow-by" caused by worn out piston rings, valves, and seals.
7. Clogged catalytic converter.
8. Faulty MAP, MAF, IAC, TPS, CPS, ETS, sensors causing ECM to compensate by changing injector timing to run excessively rich.
9. Contamination from engine coolant leaking into the system.
10. Poor fuel system performance caused by contaminated fuel, water, dirt, rust, ethanol sludge, faulty fuel pump, pressure regulator, clogged fuel filter, injectors and or wiring issues, corroded, broken or loose pins in the wiring connectors causing corrupt data being sent to the ECM.
11. A poorly tuned engine.
For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have nice a day.
What is an Oxygen Sensor and How Can It Go Bad
Auto Repair 10 Oxygen Sensors Are Critical Key to Passing Emissions
Oxygen Sensors for Preventive Maintenance
Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/gregg_c0ec1df182c7330e