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

Solution

1. Preparation

• Gather tools and parts required.
• Disconnect the battery to prevent any electrical issues.
• Allow the engine to cool before starting work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Locate the sensor on the exhaust manifold.
  2. Use the O2 sensor socket to unscrew the sensor.
  3. Install the new sensor and torque it to the manufacturer’s specifications (typically around 30 ft-lbs).
• Repeat the process for the downstream (post-catalytic) oxygen sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary)
• Remove the catalytic converter:
  1. Locate the catalytic converter in the exhaust system.
  2. Unbolt the exhaust flanges using the socket set.
  3. Cut any necessary exhaust hangers to remove the converter.
  4. Install the new catalytic converter in the reverse order, ensuring to torque the bolts to specifications (consult the service manual for exact values).

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code from the engine control module.