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

Solution

1. Preparation

• Gather tools and parts for the repair.
• Disconnect the battery to ensure safety during the repair process.
• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, oxygen sensor socket, safety goggles, gloves.

2. Replace Faulty Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors; these are typically found in the exhaust system before and after the catalytic converter.
  2. Use the oxygen sensor socket to unscrew and remove the faulty oxygen sensors.
  3. Apply anti-seize compound on the threads of the new sensors (if not pre-applied).
  4. Install the new oxygen sensors and tighten them to the manufacturer’s specifications (usually around 30 lb-ft).

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

• Sub-steps:
  1. Remove the exhaust heat shield if applicable to access the catalytic converter.
  2. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe, ensuring to keep track of any gaskets or seals.
  3. Inspect the old catalytic converter for signs of clogging or damage.
  4. Install the new catalytic converter, ensuring new gaskets are used for a proper seal.
  5. Tighten all bolts to the manufacturer’s specifications (usually around 30 lb-ft).

4. Reconnect Battery

• Reconnect the battery and clear the fault codes using the OBD-II scanner.