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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before beginning work.

2. Inspect and Repair Exhaust Leaks

• Tools Required: Socket set, exhaust sealant, or replacement gaskets
• Inspect the exhaust manifold, pipes, and connections for leaks.
• If leaks are found, repair them using exhaust sealant or replace any faulty gaskets or components.

3. Replace Faulty Oxygen Sensors

• Tools Required: O2 sensor socket, wrench, penetrating oil
• Remove the upstream and downstream oxygen sensors:
  • Apply penetrating oil to the sensor threads if they are corroded.
  • Use an O2 sensor socket to unscrew them from the exhaust system.
• Install new oxygen sensors:
  • Hand-tighten the sensors into their respective locations, then torque to manufacturer specifications (typically around 30 lb-ft).
• Reconnect the electrical connectors to the sensors.

4. Replace the Catalytic Converter (if necessary)

• Tools Required: Socket set, torch (if bolts are rusted), exhaust pipe cutter
• Remove the old catalytic converter:
  • Unbolt the catalytic converter from the exhaust system.
  • If necessary, cut the exhaust pipe to remove the converter.
• Install the new catalytic converter:
  • Position the new converter and secure it with the provided gaskets.
  • Torque the bolts to manufacturer specifications.
• Ensure all connections are secure and check for leaks.