how to fix P0420 emissions code on Honda Civic 11th Generation (2022-Present)

Solution

1. Preparation

• Gather tools and parts required for repair.
• 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 Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil.
• Locate the upstream and downstream oxygen sensors.
• Apply penetrating oil to the sensor threads and let it sit for 10-15 minutes.
• Using the O2 sensor socket, carefully remove the upstream oxygen sensor first.
• Install the new upstream oxygen sensor and torque to manufacturer's specification (usually around 30 ft-lbs).
• Repeat the process for the downstream oxygen sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed), gaskets.
• Visually inspect the catalytic converter for any signs of physical damage or excessive discoloration.
• If replacement is needed, disconnect the exhaust pipes from the catalytic converter using the socket set.
• Remove any mounting brackets holding the converter in place.
• Install the new catalytic converter, ensuring proper alignment with the exhaust system.
• Torque all bolts to the specified values and replace any gaskets as needed.

4. Reconnect Battery and Reset ECU

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear any stored codes from the vehicle's ECU.