P0420 on the 2009 Mitsubishi Lancer
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.
| TSB-12-13-005 | 2020-01-25. Service bulletin. Some affected vehicles may display an illuminated MIL with DTC P0420: Warm Up Catalyst Efficiency Below Threshold, recorded in the ECM. An incorrect parameter in the judgment criteria may cause a false MIL (mis-detection of a fault when an abnormal condition is not present). This TSB provides dealers with a procedure to reprogram the ECM with new software to correct the condition. |
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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.