OBD-II FAULT CODE
P1421

Catalyst Damage

Reference information for P1421. Because this is manufacturer-specific, confirm the exact definition for the vehicle before using the diagnostic guidance below.

Manufacturer-specific code

This code can have different meanings depending on vehicle make, model and year. Treat the definition below as a reference and confirm it with OEM service information before diagnosis or repair.

PowertrainSystem
Catalyst / exhaust emissionsCategory
MediumSeverity
  • Check Engine light
  • Poor drivability or reduced fuel economy depending on fault
  • Possible loss of power if catalyst is restricted
  • Aged catalytic converter
  • Exhaust leak
  • O2 sensor issue
  • Misfire or rich running damaging catalyst
  • Scan all modules and record freeze-frame data before clearing codes
  • Check battery voltage and related fuses
  • Check for misfires/fuel trim issues first
  • Inspect exhaust leaks and compare upstream/downstream O2 sensor activity
  • Fix engine running faults or exhaust leaks before replacing catalyst
  • Replace catalyst only after confirming it failed
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Disclaimer: Information is provided for general guidance only and may not apply to all vehicles. Always consult a qualified technician.