SOME VEHICLES MAY EXHIBIT MALFUNCTION INDICATOR LAMP ILLUMINATION WITH DIAGNOSTIC TROUBLE CODE (DTC) P0420 / 0421 OR P0430 / 0431 STORED IN MEMORY WITH NO DRIVEABILITY CONCERNS PRESENT. THIS CONDITION MAY BE CAUSED BY AN OVERLY SENSITIVE REAR OXYGEN SENSOR(S), WHICH FASELY INDICATES AN EMISSIONS CONCERN AND A DTC TO BE STORED. *TT