P0420
Sistema
Powertrain (Emissions)
Escáner necesario
Enhanced OBD2 scanner (live data graphs, freeze frame, battery voltage test)

Catalyst System Efficiency Below Threshold (Bank 1)

Understand P0420, common causes, and the right FOXWELL scanner to diagnose it.

The catalytic converter is not cleaning exhaust gases efficiently. The ECU compares upstream and downstream oxygen sensor readings and found the catalyst underperforming.

Síntomas habituales

  • Check engine light
  • Failed emissions test
  • Possible reduced fuel economy
  • Sulfur or rotten-egg smell from exhaust

Causas típicas

  • Aging or failed catalytic converter
  • Faulty downstream O2 sensor
  • Exhaust leak before the catalyst
  • Engine misfires damaging the cat
  • Oil or coolant contamination

¿Qué escáner necesita?

Enhanced OBD2 scanner (live data graphs, freeze frame, battery voltage test)

Use datos en vivo y freeze frame antes de cambiar piezas. Códigos ABS, SRS y U suelen requerir un escáner de todos los sistemas.

Consejos de diagnóstico

  • Registre el freeze frame cuando se active el código
  • Borre el código solo tras corregir la causa
  • Revise códigos pendientes relacionados
  • Verifique que la batería esté por encima de 12,4 V antes de sospechar sensores

Escáneres FOXWELL recomendados

Preguntas frecuentes

Can I diagnose P0420 with a basic code reader?
P0420 may set in the engine module, but related diagnostics often benefit from an enhanced or full-system scanner with live data and freeze frame.
Is it safe to drive with P0420?
It depends on the code and symptoms. Flashing check engine lights and misfire codes should be addressed immediately. Consult a professional if unsure.