how to fix P0420 code in Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical issues.
• Raise the vehicle and secure it on jack stands for accessibility.

Tools Required:

• OBD-II scanner
• Multimeter
• Socket set
• Torque wrench
• Jack and jack stands

2. Inspect and Replace Oxygen Sensors

• Sub-step 1: Remove the upstream oxygen sensor located before the catalytic converter using a socket wrench.
• Sub-step 2: Inspect the sensor for damage and check the connector for corrosion.
• Sub-step 3: If necessary, replace the upstream oxygen sensor with a new one, ensuring a proper seal.
• Sub-step 4: Repeat the process for the downstream oxygen sensor, located after the catalytic converter.

3. Inspect and Replace Catalytic Converter

• Sub-step 1: Remove any heat shields or brackets securing the catalytic converter.
• Sub-step 2: Unbolt the catalytic converter from the exhaust system using a socket set.
• Sub-step 3: Inspect the old catalytic converter for internal blockage or damage.
• Sub-step 4: Install the new catalytic converter, ensuring all bolts are torqued to manufacturer specifications (usually around 25-30 lb-ft).

4. Reassemble and Reconnect

• Sub-step 1: Reattach any heat shields or brackets that were removed.
• Sub-step 2: Reconnect the battery and ensure all connections are secure.

5. Clear Codes and Test

• Sub-step 1: Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
• Sub-step 2: Run the engine and let it reach operating temperature, then perform a test drive to ensure the code does not reappear.