How to Diagnose P0420

35 owner reports5 diagnostic steps~30-60 min estimated time

DIY Diagnostic Checklist

Based on 35 owner reports

Progress0%

Tools Needed

OBD Scanner

Step 1check: and or possibly clean the o2 sensors or check the cat? if so

Step 2check: engine light

Step 3check: engine light came on yesterday

Step 4check: engine light is somewhat normal for me

Step 5check: engine still on with same code

Root Causesfor P0420

Based on 35 owner reports

Confirmed Causes

1
likely the catalytic converter at fault and not worth replacing(3% of cases)catalytic-converter
2
them to be within acceptable voltages(3% of cases)

Common Misdiagnoses

What owners initially thought vs. what actually fixed the problem

sensorsi’m not fully sure(1 reports)

What Didn't Help

Repairs that owners tried but didn't fix the issue

car nerdcar persondoing truck thingsenough for torque to flag as failfamiliar withgoing to be able to get the cel fixed

Things to Check

Suggested areas to investigate based on similar cases

2-3k of that towingand or possibly clean the o2 sensors or check the cat? ifcatalytic converter converter at fault and not worth replacingengine lightengine light came on yesterdayengine light is somewhat normal for me

P0420

Catalyst System Efficiency Below Threshold (Bank 1)

mediumView full code details →

Related Guides

Required Tools

OBD Scanner