why does my Honda Accord 9th Generation (2013-2017) check engine light come on for code P0420

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors: Identify the pre-catalytic converter (upstream) and post-catalytic converter (downstream) oxygen sensors.
2. Remove Oxygen Sensors: Use an oxygen sensor socket to carefully unscrew and remove the sensors.
3. Inspect Wiring and Connectors: Check the wiring and connectors for any damage or corrosion.
4. Install New Sensors: Apply anti-seize compound to the threads of the new sensors and install them, torquing to manufacturer specifications (usually around 30 lb-ft).
5. Reconnect Battery: Reconnect the battery terminals.

3. Inspect and Replace Catalytic Converter (if needed)

1. Remove Exhaust Components: If necessary, remove any exhaust components to access the catalytic converter (use a socket set).
2. Inspect the Catalytic Converter: Check for physical damage, rattling, or blockage.
3. Install New Catalytic Converter: If replacement is required, position the new catalytic converter and secure it with the appropriate gaskets and bolts, torquing to specifications (usually around 25 lb-ft).
4. Reassemble Exhaust System: Reinstall any exhaust components removed during the process.

4. Clear Codes and Test

1. Clear Diagnostic Trouble Codes: Use the OBD-II scanner to erase the P0420 code from the vehicle’s computer.
2. Test Drive the Vehicle: Take the vehicle for a test drive to verify that the check engine light does not reappear.