Can I drive with P0420?

Yes, but drive carefully and get it checked soon. The catalytic converter is not cleaning exhaust gases as effectively as required. The car usually drives normally, but fuel economy and emissions can get worse, and it should be checked soon.

What does P0420 mean?

P0420 stands for Catalyst System Efficiency Below Threshold (Bank 1).

Symptoms you may notice

• Check engine light stays steadily illuminated
• little noticeable loss in driving power or throttle response
• Rotten egg / sulfur odor from tailpipe in some cases
• Automatic failure during state emissions inspection

How much does it cost to fix?

Repair costs for code P0420 depend on the specific underlying root cause, ranging from simple DIY checks to component replacement. The table below lists the most common causes and rough price ranges in USD:

• Aged or degraded catalytic converter
  $400-$1500 common
• Exhaust leak near or before the converter
  $50-$200 possible
• Faulty downstream oxygen sensor
  $70-$200 possible
• Engine oil or coolant burning through exhaust
  $200-$900 rare

What to do next

1. Check for exhaust leaks or rust holes near the catalytic converter flange.
2. Verify engine does not have active misfire or fuel trim codes before replacing the converter.
3. Replace the Bank 1 catalytic converter if emissions testing is required.

Related codes

About this code

Code P0420 indicates that the catalytic converter efficiency is below threshold on Bank 1. The car usually drives normally but the catalytic converter may be failing, fuel economy and emissions can get worse, and it should be checked soon.