how to fix P0420 code on Honda Civic 11th Generation (2022-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the vehicle to cool down before starting work on the exhaust system.

2. Inspect and Repair Exhaust System

• Inspect for Leaks:
  • Visually check all joints and welds in the exhaust system.
  • Use a smoke machine or spray soapy water to find leaks.
• Repair any leaks with appropriate exhaust sealant or replace damaged sections of the exhaust pipe.

3. Replace Oxygen Sensors (if needed)

• Remove Upstream O2 Sensor:

  • Locate the upstream oxygen sensor before the catalytic converter.
  • Use an O2 sensor socket to unscrew the sensor.
  • Disconnect the electrical connector.

• Install New Upstream O2 Sensor:

  • Apply anti-seize compound to the threads of the new sensor.
  • Install the new sensor and connect the electrical connector.
  • Torque to the manufacturer’s specifications (usually around 30-35 ft-lbs).

• Repeat for Downstream O2 Sensor:

  • Follow the same steps for the downstream oxygen sensor located after the catalytic converter.

4. Replace Catalytic Converter (if needed)

• Remove Old Catalytic Converter:
  • Unbolt the catalytic converter from the exhaust system using a socket set.
  • Remove any mounting brackets.
• Install New Catalytic Converter:
  • Position the new catalytic converter in place.
  • Bolt it securely and reattach any brackets.
  • Torque the bolts to the manufacturer’s specifications.

5. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and let it idle for a few minutes.
• Test drive the vehicle to ensure the P0420 code does not return.