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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down before proceeding with repairs.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Find the upstream and downstream oxygen sensors on the exhaust manifold and catalytic converter.
2. Remove the sensors: Use an oxygen sensor socket to carefully unscrew and remove both sensors.
3. Inspect the sensors: Examine the sensors for any signs of damage or corrosion. Replace if necessary.
4. Install new sensors: Apply anti-seize compound to the threads of the new sensors and install them, ensuring they are securely tightened to the manufacturer’s specifications (typically about 30 lb-ft).

3. Check and Replace the Catalytic Converter

1. Inspect the catalytic converter: Look for signs of physical damage, such as dents or holes.
2. Remove exhaust components: Use a socket set to unbolt the exhaust pipes connected to the catalytic converter. Be cautious of any rusted bolts.
3. Install the new catalytic converter: Position the new converter and tighten the bolts to the specified torque (usually around 25 lb-ft).
4. Reattach the exhaust system: Ensure all connections are secure and properly aligned.

4. Reset the ECM

1. Reconnect the battery: Attach the negative battery terminal back to the battery.
2. Clear the codes: Use the OBD-II scanner to erase the P0420 code from the ECM.
3. Start the engine: Let it idle for a few minutes to ensure all systems are functioning correctly.