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

Solution

1. Preparation

• Gather tools and parts required.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before beginning any work.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream and downstream oxygen sensors on the exhaust system.
2. Disconnect the wiring harness from both sensors.
3. Use an O2 sensor socket to remove the upstream oxygen sensor (usually located before the catalytic converter).
4. Install the new upstream oxygen sensor and torque to manufacturer specifications (typically around 30-40 ft-lbs).
5. Repeat for the downstream oxygen sensor (located after the catalytic converter).
6. Reconnect the wiring harness for both sensors.

3. Check and Repair Exhaust Leaks

1. Inspect the entire exhaust system from the exhaust manifold to the tailpipe for leaks.
2. Tighten any loose bolts or clamps.
3. If any sections are damaged, replace the affected components (e.g., gaskets, pipes).
4. Ensure all connections are sealed properly.

4. Replace the Catalytic Converter (if necessary)

1. If the catalytic converter is confirmed to be faulty, disconnect the exhaust from the catalytic converter.
2. Support the exhaust system with jack stands if necessary to prevent it from hanging.
3. Remove the catalytic converter using appropriate socket tools.
4. Install the new catalytic converter, ensuring to align it properly with the exhaust system.
5. Torque all bolts to the manufacturer's specifications.

5. Reconnect Battery and Clear Codes

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the P0420 code from the vehicle's memory.