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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the vehicle to cool down before starting work.

2. Inspect and Replace O2 Sensors (if faulty)

1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) O2 sensors.
2. Use a socket wrench to remove the O2 sensors (usually 22mm).
3. Inspect the wiring harness and connectors for damage.
4. If faulty, install new O2 sensors:
   • Align and insert the new sensor into the exhaust pipe.
   • Tighten to manufacturer specifications (typically around 30 lb-ft).
   • Reconnect the electrical connector.

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

1. Remove the exhaust components leading to the catalytic converter using a socket set (usually 10mm or 12mm bolts).
2. Inspect the catalytic converter for physical damage or blockage.
3. If replacement is needed, install the new catalytic converter:
   • Position the new converter and align it with the exhaust pipes.
   • Install and tighten bolts to the manufacturer’s torque specifications (typically around 25 lb-ft).
   • Reconnect any heat shields or brackets that were removed.

4. Clear Codes and Test

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
3. Start the engine and allow it to reach normal operating temperature.
4. Take the vehicle for a test drive to verify that the check engine light does not reappear.