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

Solution

1. Preparation

• Gather necessary tools and parts.
• Park the vehicle on a flat surface, engage the parking brake, and disconnect the battery.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream oxygen sensor (before the catalytic converter) by:
  1. Disconnecting the electrical connector.
  2. Using the O2 sensor socket to unscrew the sensor from the exhaust pipe.
• Install the new upstream oxygen sensor:
  1. Thread the new sensor into the exhaust pipe by hand to avoid cross-threading.
  2. Torque to the manufacturer's specification (typically around 30 ft-lbs).
  3. Reconnect the electrical connector.
• Repeat the process for the downstream oxygen sensor (after the catalytic converter).

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, pry bar, jack stands, torque wrench.
• Raise the vehicle safely using jack stands and remove the exhaust components as necessary to access the catalytic converter.
• Remove the bolts or clamps securing the catalytic converter to the exhaust system.
• Inspect the old catalytic converter for any signs of damage or blockage.
• Install the new catalytic converter:
  1. Position the new converter in place.
  2. Secure with bolts or clamps and torque to the manufacturer's specifications.
  3. Ensure all connections are tight and leak-free.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code from the PCM.