How many oxygen sensor on a 02 chevy blazer - 2002 Chevrolet Blazer

No, there are only 3 oxygen sensors on a 2002 Blazer V6. 1 one the drivers side just below the exhaust mainfold on the exhaust pipe. And 1 on the passenger side exhuast pipe just before the Y connection of both left and right pipes. And 1 after the catalytic converter.

I had a check engine light on for about 2 years, After one year, I had it checked at advanced AP, It showed bank 2 position 1. They told me I have 4 Oxygen sensors, and that Bank 2 position 1 should be the one in front of the catalytic converter. Well one thing is, still did not replace it, and yes gas economy went down a bit, but no rough idle yet. (When your sensor goes out, the computer goes into a looping mode to run your vehicle. But does not get feed back to improve performance.) Anyway, Yesterday decided get a scan again at Advanced, still the same Oxygen sensor was at fault. I looked and looked and never found a forth O2 sensor. Looked in the haynes manual, and it clarified that there were only 3 o2 sensors. No, there are only 3 oxygen sensors on a 2002 Blazer V6. 1 one the drivers side just below the exhaust mainfold on the exhaust pipe. And 1 on the passenger side exhuast pipe just before the Y connection of both left and right pipes. And 1 after the catalytic converter. I had a check engine light on for about 2 years, After one year, I had it checked at advanced AP, It showed bank 2 position 1. They told me I have 4 Oxygen sensors, and that Bank 2 position 1 should be the one in front of the catalytic converter. Well one thing is, still did not replace it, and yes gas economy went down a bit, but no rough idle yet. (When your sensor goes out, the computer goes into a looping mode to run your vehicle. But does not get feed back to improve performance.) Anyway, Yesterday decided get a scan again at Advanced, still the same Oxygen sensor was at fault. I looked and looked and never found a forth O2 sensor. Looked in the haynes manual, and it clarified that there were only 3 o2 sensors.