P0420
System
Powertrain (Emissions)
Scanner som krävs
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.

Vanliga symptom

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

Typiska orsaker

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

Vilken scanner behöver du?

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

Använd live-data och freeze frame innan du byter delar. ABS-, SRS- och U-koder kräver oftast en fullsystems-scanner.

Diagnostiktips

  • Spara freeze frame när koden först sätts
  • Rensa koden först efter att orsaken är åtgärdad
  • Kontrollera relaterade väntande koder
  • Verifiera batterispänning över 12,4 V innan du misstänker sensorer

Rekommenderade FOXWELL-scannrar

Vanliga frågor

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.