how to fix P0420 code on Honda Accord 10th Generation (2018-2022)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to ensure safety.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Use an O2 sensor socket and ratchet to unscrew the sensor.
  2. Disconnect the wiring harness from the sensor.
• Install the new upstream oxygen sensor:
  1. Apply anti-seize compound to the threads of the new sensor.
  2. Screw in the sensor by hand, then tighten to manufacturer specifications (usually around 30 lb-ft).
  3. Reconnect the wiring harness.
• Repeat for the downstream (post-catalytic) oxygen sensor if necessary.

3. Inspect and Replace the Catalytic Converter (if necessary)

• Remove the catalytic converter:
  1. Loosen and remove any mounting bolts or clamps securing the catalytic converter to the exhaust system using a socket set.
  2. Carefully detach the catalytic converter from the exhaust pipe.
• Install the new catalytic converter:
  1. Position the new catalytic converter in place, ensuring proper alignment with the exhaust system.
  2. Reinstall and tighten all mounting bolts or clamps to the manufacturer's torque specifications (typically around 25-35 lb-ft).

4. Clear Codes and Test

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and allow it to reach operating temperature.
• Conduct a test drive to see if the check engine light reappears.