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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical issues.

2. Remove Exhaust Components

• Tools Required: Socket set, jack and jack stands, penetrant spray
• Raise the vehicle with a jack and secure it with jack stands.
• Spray penetrant on the exhaust bolts to loosen rusted connections.
• Carefully unbolt and remove the exhaust components leading to the catalytic converter (e.g., exhaust manifold, exhaust pipe).

3. Inspect and Replace Catalytic Converter

• Inspect the catalytic converter for any physical damage or blockage.
• If replacement is necessary:
  • Tools Required: Torque wrench, gaskets
  • Remove the old catalytic converter by unbolting it from the exhaust system.
  • Install the new catalytic converter, ensuring that any gaskets are replaced.
  • Torque the bolts to the manufacturer-recommended specifications (check repair manual for exact values).

4. Reinstall Exhaust Components

• Reattach the exhaust components removed in Step 2.
• Ensure all bolts are tightened to the correct torque specifications.

5. Check Oxygen Sensors

• If the oxygen sensors were found to be faulty during diagnostics, replace them.
• Tools Required: O2 sensor socket
• Install new oxygen sensors where applicable, ensuring proper torque is applied.

6. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0420 code and any other stored codes.