Q: Check Engine Light and O2 sensor on a used car

Hi there. Assuming the vehicle Check Engine Light is an O2 sensor code does not necessarily mean the O2 sensor is at fault. It could be an electrical fault in the O2 sensor circuit(s). I highly recommend that you have the vehicle properly inspected by a certified technician, such as one from YourMechanic, if you are seriously considering buying the car. They will be able to give you a precise diagnosis on the problem and can conduct a full inspection on the car to unravel any faults that may not be apparent. If you would simply like an estimate for the oxygen sensor replacement, you can enter the vehicle information on our estimator page for a quote.