[Davescort97]

Your Tracer has 2 Oxygen sensors. One upstream in the exhaust manifold and one downstream after the catalytic converter. 9 times out of 10 the up stream sensor should be replaced when you are getting a code. If you have over 85k it is time to do it. It will increase your gas mileage 10-20%. If you unplugged the upstream sensor it will cause a code for the downsteam sensor. The two are related. If you're getting a code off and on you might check the wires to the O2 sensors. Get that upstream sensor before you do anything else.