how to fix Honda Civic 10th Generation (2016-2021) P0420 code for catalytic converter

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to avoid any electrical issues.
• Raise the vehicle using a jack and secure it on jack stands.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream oxygen sensor:
  1. Locate the upstream O2 sensor (before the catalytic converter).
  2. Use the O2 sensor socket to unscrew it from the exhaust manifold.
  3. Inspect the sensor for damage; replace if necessary.
• Install the new upstream oxygen sensor:
  1. Apply anti-seize compound to the threads of the new sensor.
  2. Hand-tighten the sensor, then use a torque wrench to tighten to the manufacturer’s specifications (usually around 30-40 lb-ft).
• Repeat the process for the downstream oxygen sensor (after the catalytic converter) if it was found faulty.

3. Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool, penetrating oil.
• Remove the old catalytic converter:
  1. Locate and unbolt the catalytic converter from the exhaust system using the socket set.
  2. Use the exhaust hanger removal tool to detach it from any hangers supporting it.
  3. Carefully remove the catalytic converter from the vehicle, ensuring not to damage surrounding components.
• Install the new catalytic converter:
  1. Position the new catalytic converter in place and connect it to the exhaust system.
  2. Bolt it securely using the original or new hardware, tightening to manufacturer specifications.
  3. Reattach any exhaust hangers as needed.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.