Symptom hub
Catalyst Code After a Misfire: Converter Failure or Misfire Aftermath?
When a catalyst-efficiency code shows up after a known misfire event, the smartest first question is not whether the converter is bad. It is whether the catalyst was actually damaged, temporarily overwhelmed by raw fuel, or simply being evaluated before the upstream misfire and mixture problem were truly solved.
Likely related codes
Start your diagnostic path here
P0300 — Random/Multiple Cylinder Misfire Detected P0171 — System Too Lean (Bank 1) P0172 — System Too Rich (Bank 1) P0420 — Catalyst System Efficiency Below Threshold (Bank 1) P0430 — Catalyst System Efficiency Below Threshold (Bank 2) P0421 — Warm Up Catalyst Efficiency Below Threshold (Bank 1) P0431 — Warm Up Catalyst Efficiency Below Threshold (Bank 2)