P0420 on the 2000 Mazda Millenia
The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.
Nobody has written a description of this code yet.
| 0100301 | 2001-07-09. Service bulletin. 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 |
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1 on file from NHTSA, as of 2026-10-19. See them in the bulletin list. A bulletin lists model years: read the document for which vehicles it concerns.