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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface.
• Disconnect the battery to prevent any electrical shorts.

2. Inspect Exhaust System

• Tools Required: Socket set, pry bar
• Check for any visible cracks or holes in the exhaust pipes and joints.
• Tighten any loose connections and replace damaged components as necessary.

3. Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, torque wrench
• Remove the upstream (pre-catalytic converter) O2 sensor by using the O2 sensor socket.
• Install the new upstream O2 sensor and torque it to the manufacturer's specifications (usually around 30-40 ft-lbs).
• Repeat the process for the downstream (post-catalytic converter) O2 sensor.

4. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, cutting tools (if needed), jack and jack stands
• Remove the catalytic converter by loosening the bolts or nuts securing it to the exhaust manifold and the exhaust pipe.
• Inspect the old catalytic converter for damage or clogging. If it is damaged or restricted, replace it with a new one.
• Install the new catalytic converter and 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 vehicle and conduct a test drive to ensure the issue is resolved.