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

Solution

1. Preparation

• Gather tools and materials needed for repair.
• Disconnect the negative battery terminal to prevent any electrical shorts.

2. Inspect Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter
• Sub-steps:
  1. Remove the downstream oxygen sensor from the catalytic converter.
  2. Use a multimeter to check the resistance and ensure it is within manufacturer specifications.
  3. If faulty, replace the oxygen sensor with a new one.

3. Check Catalytic Converter

• Tools Required: Back pressure gauge, wrench set
• Sub-steps:
  1. Attach a back pressure gauge to the exhaust system before the catalytic converter.
  2. Start the engine and observe the back pressure reading; it should be within acceptable limits.
  3. If the back pressure is too high, replace the catalytic converter.

4. Repair Exhaust Leaks

• Tools Required: Exhaust sealant, clamps, or new exhaust gaskets
• Sub-steps:
  1. Inspect the exhaust system for leaks, particularly around joints and connections.
  2. If leaks are found, use exhaust sealant or replace gaskets/clamps as necessary.
  3. Ensure all connections are tight and secure to prevent further leaks.

5. Reassemble and Test

• Tools Required: Ratchet and socket set
• Sub-steps:
  1. Reinstall any components that were removed during the inspection.
  2. Reconnect the negative battery terminal.
  3. Clear the error codes using the OBD-II scanner.
  4. Start the engine and perform a test drive to ensure the issue is resolved.