how to fix a P0420 code on my Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the vehicle's battery to ensure safety.
• Allow the engine to cool before starting work.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream and downstream oxygen sensors: These are typically located on the exhaust manifold and after the catalytic converter.
2. Remove the oxygen sensors: Use an oxygen sensor socket and ratchet to unscrew and remove each sensor.
3. Inspect the sensor condition: Check for any signs of damage or fouling on the sensors.
4. Install new oxygen sensors: Apply anti-seize compound to the threads of the new sensors, then install and torque to the manufacturer's specifications (usually around 30 lb-ft).

3. Inspect and Replace Catalytic Converter

1. Locate the catalytic converter: It is usually mounted in the exhaust system, after the exhaust manifold.
2. Remove the catalytic converter: Disconnect the exhaust pipes connected to both ends. Use a socket set to remove the bolts or clamps holding it in place.
3. Inspect for damage: Check for any physical blockages or signs of overheating.
4. Install a new catalytic converter: Ensure it is compatible with your specific model. Secure it with bolts and/or clamps, and torque to the manufacturer's specifications.

4. Reconnect Battery and Clear Codes

1. Reconnect the battery: Ensure all connections are secure.
2. Use the OBD-II scanner: Clear the P0420 code from the vehicle's computer.

5. Test Drive

1. Perform a test drive: Drive the vehicle under various conditions to ensure the check engine light does not reappear.