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

Solution

1. Preparation

• Gather tools and parts.
• Ensure the vehicle is parked on a flat surface, and the engine is cool.
• Disconnect the battery's negative terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors (if necessary)

1. Locate the Oxygen Sensors:

   • The upstream (pre-catalytic converter) sensor is typically located on the exhaust manifold.
   • The downstream (post-catalytic converter) sensor is located after the catalytic converter.

2. Remove the Sensors:

   • Use an O2 sensor socket and ratchet to unscrew the sensors.
   • Carefully disconnect the electrical connectors from the sensors.

3. Install New Sensors:

   • Apply anti-seize compound on the threads of the new oxygen sensors (if not pre-applied).
   • Install the new sensors by screwing them into place and tightening to the manufacturer’s specified torque (usually around 30 Nm or 22 lb-ft).
   • Reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Inspect the Catalytic Converter:

   • Check for dents, cracks, or any signs of damage that may affect performance.
   • Look for any rattling sounds indicating internal failure.

2. Remove the Catalytic Converter:

   • Use a socket set to remove the bolts securing the catalytic converter to the exhaust system.
   • Carefully remove the converter and any gaskets that may need replacing.

3. Install New Catalytic Converter:

   • Position the new catalytic converter and secure it with the bolts.
   • Replace gaskets as necessary to prevent exhaust leaks.
   • Torque the bolts to the manufacturer’s specifications.

4. Clear the Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the ECM.