how to fix P0420 code in Honda Accord Eleventh Generation (2023-present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down before working on the exhaust system.

2. Inspect and Replace O2 Sensors

• Tools Required: O2 sensor socket, wrench set.
• Remove the upstream (pre-catalytic) O2 sensor using the O2 sensor socket.
• If the sensor is found faulty (voltage output out of range), replace it with a new one.
• Install the new O2 sensor and torque it to the manufacturer’s specifications (typically around 30 ft-lbs).
• Repeat the process for the downstream (post-catalytic) O2 sensor if necessary.

3. Inspect and Clean or Replace Catalytic Converter

• Tools Required: Socket set, exhaust hanger removal tool, torque wrench.
• Locate the catalytic converter and visually inspect it for any signs of damage (cracks, dents).
• If the converter is clogged or damaged, it may need replacement.
• If cleaning is required, use a catalytic converter cleaner and follow the manufacturer's instructions.
• If replacing, unbolt the catalytic converter from the exhaust system carefully and replace it with a new unit. Torque bolts to specified values (usually around 40 ft-lbs).

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the ECU.
• Start the engine and allow it to reach operating temperature.
• Perform a test drive to monitor the vehicle's performance and ensure the check engine light does not reappear.