how to fix P0420 code on Honda Accord Eleventh Generation (2023-present)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative terminal from the battery to ensure safety.
• Allow the vehicle to cool down before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:
   • Locate the sensor before the catalytic converter.
   • Use an oxygen sensor socket to unscrew and remove the sensor.
2. Install the new upstream oxygen sensor:
   • Apply anti-seize compound on the threads of the new sensor.
   • Screw the new sensor in place and tighten to manufacturer specifications (typically 30 Nm).
3. Repeat for the downstream oxygen sensor if necessary.

3. Inspect and Replace Catalytic Converter (if needed)

1. Remove the exhaust components:
   • Depending on design, you may need to remove heat shields or other exhaust sections.
   • Use a socket set and ratchet to remove bolts.
2. Remove the catalytic converter:
   • Detach the catalytic converter from the exhaust system and any oxygen sensors attached.
3. Install the new catalytic converter:
   • Position the new converter and secure it with the original or new bolts.
   • Torque bolts to manufacturer specifications (typically 40 Nm).
4. Reattach any components removed during disassembly.

4. Reconnect Battery and Test

1. Reconnect the negative terminal of the battery.
2. Start the engine and allow it to idle for a few minutes.
3. Use the OBD-II scanner to clear the P0420 code and check for any reoccurrence.