P0420 on the 1999 Toyota Sienna
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.
| EG00299 | 1999-08-12. Service bulletin. REVISED INFORMATION TO ASSIST IN THE DIAGNOSIS OF DIAGNOSTIC TROUBLE CODE P0420 INDICATING A POSSIBLE CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD CONDITION. *TT |
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| 031199 | 1999-06-03. Service bulletin. BRIEF INFORMATION REGARDING DIAGNOSTIC TROUBLE CODE P0420 INDICATING A POSSIBLE CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD CONDITION. *TT |
| EG00299 | 1999-05-11. Service bulletin. SOME VEHICLES MAY EXHIBIT DIAGNOSTIC TROUBLE CODE P0420 INDICATING A POSSIBLE CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD CONDITION. *TT |
3 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.