how to fix P0420 code on Honda Accord 8th Generation (2008-2012)

Solution

1. Preparation

• Gather tools and parts needed for repairs.
• Safety glasses and gloves should be worn.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Repair Exhaust Leaks

• Sub-steps:
  1. Start the vehicle and listen for exhaust leaks around the exhaust system.
  2. Use a spray bottle with soapy water to identify leaks; bubbles will form at the leak points.
  3. Tighten loose connections or replace damaged gaskets or pipes.

3. Test and Replace Oxygen Sensors (if necessary)

• Sub-steps:
  1. Remove the upstream and downstream O2 sensors using an O2 sensor socket.
  2. Install new O2 sensors and torque them to the manufacturer’s specifications (typically around 30 lb-ft).
  3. Reconnect the wiring harness to the sensors.

4. Inspect and Replace Catalytic Converter (if needed)

• Sub-steps:
  1. Remove the catalytic converter from the exhaust system, noting the orientation.
  2. Inspect the catalyst for signs of melting or clogging.
  3. Install the new catalytic converter, ensuring proper alignment and sealing.
  4. Torque the mounting bolts to the manufacturer’s specifications (consult repair manual).

5. Reconnect Battery and Clear Codes

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.