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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down before starting work on the exhaust system.

2. Inspect and Replace Sensors

• Tools Required: O2 sensor socket, wrench set, torque wrench
• Remove the upstream and downstream oxygen sensors using the O2 sensor socket.
• Inspect the connectors and wiring for damage; replace if necessary.
• Install new oxygen sensors and torque them to the manufacturer's specifications (typically around 30-40 ft-lbs).

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter
• Raise the vehicle securely on jack stands.
• Remove any clamps or bolts securing the exhaust system before the catalytic converter.
• Use an exhaust pipe cutter to remove the old catalytic converter if necessary.
• Install the new catalytic converter, ensuring proper alignment and sealing.
• Reattach any clamps or bolts and torque them to specification.

4. Clear Codes and Test

• Tools Required: OBD-II scanner
• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and allow it to reach operating temperature.
• Perform a test drive to ensure the check engine light does not reappear.