P0420 on the 1998 GMC Sonoma
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.
| 040605001 | 2005-01-03. Service bulletin. SERVICE ENGINE SOON (SES) LIGHT ILLUMINATED, DIAGNOSTIC TROUBLE CODE P0420 SET. *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.