📖 What Does P0420 Mean?
The catalytic converter on bank 1 is not operating efficiently. The oxygen sensors before and after the catalytic converter are showing similar readings, indicating the catalyst is not properly cleaning the exhaust gases.
Symptoms
Check engine light, failed emissions test, reduced fuel economy, sulfur smell from exhaust, poor engine performance at higher RPMs.
Common Causes
Failed catalytic converter, faulty oxygen sensors, exhaust leaks before catalytic converter, engine running too rich or lean, oil contamination in exhaust system.
Possible Solutions
Replace catalytic converter, install new oxygen sensors, repair exhaust leaks, fix fuel mixture issues, address oil burning problems, use catalytic converter cleaner as temporary measure.
Recommended Parts & Tools
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📦 Parts Needed
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Frequently Asked Questions about P0420
How serious is P0420?
This code has a medium severity level. This should be diagnosed and repaired soon to prevent further issues.
Can I drive with P0420?
You can typically drive short distances, but have it diagnosed as soon as possible.
How much does it cost to fix P0420?
Repair costs vary depending on the root cause, but typically range from $100-300 including parts and labor.
Related Diagnostic Codes
Other codes that may appear with P0420
System Too Lean Bank 1
System Too Rich Bank 1
System Too Lean Bank 2
System Too Rich Bank 2
Catalyst System Efficiency Below Threshold Bank 2
💡 Why These Codes Are Related:
- • Similar Issues: Same root cause or component failure
- • Related Problems: Often occur together due to system interactions
- • Sequential Codes: Progressive failure stages or multiple sensors
- • Same System: Components within the same automotive system