Diagnostic group

Catalyst Efficiency Codes

Catalyst monitor codes that compare upstream and downstream oxygen-sensor activity to judge converter efficiency.

P0420-P0434

How to Use This Group

Start by reading all stored and pending codes together. A companion lean, misfire, EVAP, or oxygen-sensor code can change which test should come first.

Codes in This Group

P0420 Catalyst System Efficiency Below Threshold, Bank 1 The PCM sees downstream oxygen-sensor behavior that suggests bank 1 catalyst efficiency is below threshold. P0430 Catalyst System Efficiency Below Threshold, Bank 2 The PCM sees downstream oxygen-sensor behavior that suggests bank 2 catalyst efficiency is below threshold.

Sources

  1. SAE J2012DA Digital Annex of Diagnostic Trouble Code Definitions
  2. 1996 Ford Mustang Owner Guide