How many o2 sensors does a 1999 Chevy s10 have?

A 1999 Chevy S10 typically has one O2 sensor in the exhaust system before the catalytic converter. However, some models with more advanced emissions systems *might* have a second downstream sensor (after the catalytic converter). To be certain, you should check your specific vehicle's repair manual or consult a parts store using your VIN number.