how to fix P0420 catalyst efficiency below threshold in Honda Accord 10th Generation (2018-2022)?

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, jack and jack stands, temperature gun, multimeter, safety goggles, gloves.
• Ensure the vehicle is parked on a level surface and the engine is cool. Disconnect the battery to prevent electrical shock.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Disconnect the electrical connectors from both oxygen sensors.
  3. Using the appropriate socket, remove both sensors from the exhaust system.
  4. Install new oxygen sensors in the same locations, ensuring they are tightened to manufacturer specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter

• Sub-steps:
  1. Locate the catalytic converter in the exhaust system.
  2. Use a socket set to remove any bolts securing the catalytic converter to the exhaust pipes.
  3. Carefully lower the catalytic converter from its position (may require a jack if heavy).
  4. Inspect the old catalytic converter for signs of damage or clogging.
  5. Install the new catalytic converter, ensuring that all gaskets are in place. Tighten bolts to manufacturer torque specifications (typically around 40 lb-ft).

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear any diagnostic trouble codes.