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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, jack and jack stands, safety goggles, gloves.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Inspect Exhaust System

• Sub-steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Visually inspect the exhaust system from the front to the rear for any signs of leaks, corrosion, or damage.
  3. Tighten any loose connections and replace any damaged components.

3. Check Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Use a multimeter to measure the voltage output of each sensor (should be between 0.1 to 0.9 volts for upstream during normal operation).
  4. If any sensor is faulty, replace it with a new one.

4. Inspect and Replace Catalytic Converter

• Sub-steps:
  1. If no issues were found with the oxygen sensors, inspect the catalytic converter for blockage or damage.
  2. If necessary, remove the catalytic converter by unbolting it from the exhaust system.
  3. Install a new catalytic converter, ensuring all gaskets are replaced and bolts are torqued to manufacturer specifications.
  4. Reconnect all components and sensors.

5. Clear Codes and Test Drive

• Sub-steps:
  1. Use the OBD-II scanner to clear the P0420 code from the ECM.
  2. Start the engine and perform a test drive to monitor performance and check for the reappearance of the check engine light.