Question

What is the code P0420 on a Honda?

P0420 code Honda is defined as “Catalyst System Efficiency Below Threshold (Bank 1),” meaning the efficiency of the catalyst system is lower than the threshold on Bank 1.

So, when this code shows up, your car’s catalytic converter won’t convert exhaust pollutants efficiently, resulting in higher emissions. The powertrain control module (PCM) finds out the issue by comparing data from the upstream and downstream oxygen sensors. The code usually appears on models like the CR-V and Accord.

What are the symptoms of code P0420 Honda?

The most clear symptom is the check engine light turned on. These are some other signs you can observe.

• Decreased fuel economy
• Engine performance drops
• Failed emissions test
• Rotten egg smell from the exhaust

What causes Honda DTC P0420?

These are some reasons why the error code shows up in your car.

• Damaged catalytic converter
• Defective oxygen sensors
• Fuel system issues
• Misfiring engine
• Exhaust leakage

How to fix the P0420 code in a Honda

The following repairs can help you fix the error code.

• Replace the catalytic converter
• Replace the defective oxygen Sensors
• Repair the exhaust if there’s leakage
• Replace the ignition coil or spark plugs to fix the misfiring engine
• Clean the fuel injectors

Is it safe to drive a Honda with a P0420?

No, it isn’t safe to drive with this engine code for a long period. As the code implies an issue with the catalytic converter, driving for long can cause possible damage to the engine or catalytic converter, resulting in decreased fuel economy and higher emissions. The repair cost ranges between $50 and $3,000.

What does code P0420 mean on a Honda Accord?

P0420 Honda Accord​ implies “Catalyst System Efficiency Below Threshold (Bank 1),” meaning the powertrain control module sensed that the catalytic converter’s Bank 1 is failing.