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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to avoid electrical shorts.
• Allow the engine to cool if it has been running.

2. Replace Oxygen Sensors (if defective)

• Tools Required: O2 sensor socket, wrench, penetrating oil
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors.
  2. Apply penetrating oil to the sensor threads and allow it to soak.
  3. Disconnect the electrical connectors from the sensors.
  4. Use the O2 sensor socket to remove the sensors from the exhaust system.
  5. Install the new sensors by screwing them in hand-tight, then torque to specifications (usually around 30 lb-ft).
  6. Reconnect the electrical connectors securely.

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

• Tools Required: Socket set, torque wrench, exhaust gasket, jack stands
• Sub-steps:
  1. Raise the vehicle and secure it on jack stands.
  2. Remove any heat shields covering the catalytic converter.
  3. Use the socket set to unbolt the catalytic converter from the exhaust manifold and the exhaust pipe.
  4. Inspect the old catalytic converter for physical damage or blockage.
  5. Install the new catalytic converter with a new gasket, ensuring proper alignment.
  6. Torque the bolts to manufacturer specifications (typically around 40 lb-ft).
  7. Reattach heat shields if applicable.