My car burns pretty rich, found an exhaust leak, fixed it. Does one o2 sensor influence the PCM more than the other as far as leaning or adding fuel? Buget allows only one at a time--sensors are old--So Bank 1 or Bank 2. Bosh ok ? Thanks in advance Dwayne

 

Each pre-cat sensor helps the PCM control the A/F ratio in one bank of the engine. You would replace the sensor on the side that is running rich. Before replacing anything, it would be a good idea to determine if the problem is due to a faulty sensor, or due to some other cause that's causing the O2 sensor to provide incorrect data to the PCM. If you had an exhaust leak, that would cause that bank of the engine to run rich. Repairing the leak should correct the problem.

Then there's the after-cat sensors, and they play no part at all in how the PCM sets the A/F ratio.

Use only the OEM AC//Delco (Delphi) sensors. You can get them for about $35 from the online GM parts sources that are mentioned frequently on this site.