how to solve the P0420 code on my Honda Civic 10th Generation (2016-2021)?

Solution

1. Preparation

• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Gather tools and parts required for repair.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter
• Remove the upstream (pre-catalytic converter) oxygen sensor by using the O2 sensor socket.
• Check the condition of the sensor; if it shows signs of damage or corrosion, replace it with a new one.
• Reinstall the new oxygen sensor and reconnect the wiring harness.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, exhaust clamp tool
• Remove any heat shields or brackets securing the catalytic converter.
• Disconnect the exhaust piping connected to the catalytic converter using the socket set.
• Inspect the catalytic converter for any physical blockage or damage. If damaged, replace it with an OEM or compatible aftermarket catalytic converter.
• Reinstall the new catalytic converter, ensuring all connections are secure and leak-free.

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal and use the OBD-II scanner to clear any trouble codes.
• Start the engine and allow it to reach operating temperature.
• Take the vehicle for a test drive to monitor performance and check if the check engine light reappears.