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

Solution

1. Preparation

• Gather necessary tools and materials.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts during the repair.

2. Inspect and Replace Oxygen Sensors

• Steps:
  1. Locate the upstream and downstream oxygen sensors.
  2. Disconnect the wiring harness from the sensors.
  3. Using an O2 sensor socket, remove the sensors from the exhaust pipe.
  4. Install new oxygen sensors, ensuring to follow the manufacturer's torque specifications (typically around 30 ft-lbs).
  5. Reconnect the wiring harness securely.

3. Inspect and Replace the Catalytic Converter (if necessary)

• Steps:
  1. Visually inspect the catalytic converter for physical damage or signs of clogging.
  2. If replacement is needed, unbolt the exhaust piping connected to the catalytic converter using a socket set.
  3. Remove the old catalytic converter from the vehicle.
  4. Install the new catalytic converter, ensuring all gaskets are in place and the bolts are torqued to the specified value (usually around 25-30 ft-lbs).
  5. Reconnect the exhaust piping and check for leaks.

4. Reset the Engine Control Module (ECM)

• Steps:
  1. Reconnect the battery terminals.
  2. Use the OBD-II scanner to clear the P0420 code from the ECM.
  3. Start the engine and allow it to idle for a few minutes.