what to do if my Honda Accord has a code P0420

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to avoid electrical shorts.
• Allow the exhaust system to cool down before handling.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, ratchet, and torque wrench.
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Disconnect the electrical connector.
  2. Use an O2 sensor socket to unscrew the sensor.
  3. Install the new sensor, ensuring it is torqued to manufacturer specifications (usually around 30 lb-ft).
• Repeat the process for the downstream (post-catalytic) oxygen sensor if it is also faulty.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, exhaust hanger tool, cutting tool (if needed), and torque wrench.
• Remove the catalytic converter:
  1. Support the exhaust system with jack stands.
  2. Remove any heat shields if applicable.
  3. Disconnect the exhaust pipes at both ends of the catalytic converter.
  4. Remove any mounting bolts or clamps securing the converter.
  5. If the converter is welded in place, cut it out using a cutting tool.
• Install the new catalytic converter:
  1. Position the new converter in place.
  2. Reattach the exhaust pipes and securely fasten with bolts or clamps, torquing to manufacturer specifications.
  3. Reinstall any heat shields removed earlier.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code and any other stored codes.