Catalytic Converter Failure
Converters fail from age, contamination by oil or coolant, or misfires. Symptoms are a rotten-egg smell, less power and a P0420 code.
Can I drive it? Drive with care
A clogged converter can overheat and choke the engine. Drive gently and get it diagnosed.
Typical repair cost
$900-$2,500 depending on the car, more in states that require CARB-approved parts.
General US estimates, not quotes. Prices vary by region, vehicle and shop.
Symptoms to Look For
These signs indicate you might be experiencing this issue
- Check engine light (P0420 code common)
- Rotten egg smell from exhaust
- Reduced engine performance
- Rattling noise from under car
- Failed emissions test
Potential Causes
Most likely reasons for this problem, sorted by probability
Repair Solutions
Step-by-step instructions to diagnose and fix the problem
1Catalytic Converter Diagnosis
- 1
Scan for trouble codes (P0420, P0430)
- 2
Check exhaust backpressure
- 3
Inspect converter for physical damage
- 4
Check engine for issues causing contamination
- 5
Replace converter if failed
Need professional help?
Find a repair shop near you, or describe your exact symptoms to the AI mechanic
When to See a Mechanic
Do not wait if any of these apply
- Noticeable power loss
- A rattle from under the car
- A rotten-egg smell
How to Prevent It
Simple habits that stop this problem coming back
- Fix misfires quickly
- Fix oil or coolant burning quickly
- Use only cat-safe fuel additives
Frequently Asked Questions
How long does a catalytic converter last?
Often 100,000 miles or more when the engine runs well.
Can I clean a catalytic converter?
Cleaners rarely fix a failed converter. Diagnose first, because P0420 can also come from O2 sensors or an exhaust leak.
Related Trouble Codes
Codes a scan tool may show with this problem
Related Issues
AI-generated and informational only. This is not a diagnosis of your specific vehicle and does not replace inspection by a qualified technician.