Testing my 2003 Buick Century gave code P0138. What to check first and possibly replace myself?

Question

Testing my 2003 Buick Century gave code P0138. What should I check first and possibly replace myself?

Answer 1

most likely oxygen sensor on Bank 1 Sensor 2 is bad. if you dont have any other problems related to fuel pressure or injector problems replacing the sensor will fix it. The sensor is under the car so it would be hard to do it yourself without all the proper tools and lifting the car up. Labor should be around $40 or so at a mechanic shop