how to fix P0420 Honda Accord 10th Generation (2018-2022) catalyst system issue

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet and extension, torque wrench.
• Steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Unplug the electrical connectors from both sensors.
  3. Use the O2 sensor socket to remove the sensors from the exhaust system.
  4. Apply anti-seize compound (if specified) to the threads of the new sensors.
  5. Install the new sensors and torque to manufacturer specifications (typically around 30 ft-lbs).
  6. Reconnect the electrical connectors.

3. Replace Catalytic Converter (if needed)

• Tools Required: Socket set, torque wrench, exhaust gasket, exhaust clamp.
• Steps:
  1. Loosen and remove the bolts securing the catalytic converter to the exhaust manifold and exhaust pipe.
  2. Remove any brackets or hangers that may obstruct the removal of the catalytic converter.
  3. Inspect the exhaust gasket and replace it if damaged.
  4. Install the new catalytic converter and secure it with bolts, torquing to manufacturer specifications (typically around 40-50 ft-lbs).
  5. Reinstall any brackets or hangers removed earlier.

4. Clear Error Codes

• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
• Reconnect the battery if it was disconnected.