My check engine light is on. I checked the code, 2 blinks on the LED. I understand that this is the O2 Sensor. I purchased the car with 60k and now have over 100K miles. I don't think they have ever been replaced so I am hoping this will solve the problem. California Smog due in April and it will not pass with light on. How many sensors are there? Can I change these myself? New Wiring Harness last year.