what does code P0420 mean for Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

• Gather necessary tools and materials.
• Disconnect the battery to prevent electrical shorts while working on the vehicle.
• Raise the vehicle and secure it on jack stands if accessing the exhaust system from underneath.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter
• Remove the upstream (pre-catalytic converter) oxygen sensor using the O2 sensor socket.
• Inspect the sensor for damage or contamination; replace if necessary.
• Repeat the process for the downstream (post-catalytic converter) oxygen sensor.
• Ensure proper torque (typically around 30 lb-ft) when reinstalling the sensors.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, cutting tool (if necessary)
• Inspect the catalytic converter for any signs of physical damage or blockage.
• If replacement is needed, unbolt the catalytic converter from the exhaust system.
• If welded, use a cutting tool to remove the damaged catalytic converter.
• Install the new catalytic converter, ensuring all gaskets are replaced and the bolts are torqued to the manufacturer's specifications (usually around 25 lb-ft).
• Reconnect any exhaust hangers or brackets that were removed during the process.

4. Final Checks

• Reconnect the battery terminals.
• Clear the error codes using an OBD-II scanner and perform a test drive to verify that the check engine light does not reappear.