How many o2 sensors does the 2005 Chevy Equinox have?

The 2005 Chevy Equinox has two different O2 sensors. One is located on the down pipe from the headers before the catalytic converter and the other one is located on the exhaust after the cat. The O2 sensors are used to measure the exhaust gasses from Your engine to make sure that they fall within the normal operating range. Usually when one of them has a problem You will get a check engine light on at Your dash. When an O2 sensor is not working You also usually will notice that Your engine runs very rough. This is because the ECU is not getting all the information on the air to fuELRatios so it does not know how much to add to the engine.