what causes a check engine light with P0420 in my Honda Civic 10th Generation (2016-2021)?

Solution

1. Preparation

• Gather tools and parts required.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent any electrical issues during repairs.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Disconnect the electrical connectors from the oxygen sensors.
  3. Use the O2 sensor socket to remove the sensors from their respective locations.
  4. Install new oxygen sensors and torque them to the manufacturer's specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed)
• Sub-steps:
  1. Inspect the catalytic converter for physical damage or clogging.
  2. If replacement is needed, disconnect the exhaust pipes connected to the catalytic converter.
  3. Remove any mounting bolts or clamps securing the catalytic converter using a socket set.
  4. Remove the old catalytic converter and install the new one, ensuring the proper alignment.
  5. Torque the mounting bolts to the manufacturer's specifications (typically around 40 lb-ft).
  6. Reconnect the exhaust pipes and any clamps securely.

4. Reset the Check Engine Light

• After repairs, reconnect the battery.
• Use the OBD-II scanner to erase the P0420 code and reset the check engine light.