how to fix Honda Accord 10th Generation (2018-2022) check engine light P0420

Solution

1. Preparation

• Gather tools and parts required for repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

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. Remove the electrical connector from each sensor.
  3. Using the O2 sensor socket, unscrew the upstream sensor and replace it with a new one, torqued to manufacturer specifications (typically 30-40 lb-ft).
  4. Repeat the process for the downstream sensor if it is also faulty.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if applicable)
• Sub-steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Inspect the catalytic converter for signs of damage or blockage; if necessary, remove it by unbolting the exhaust pipes connected to it.
  3. If replacement is required, install the new catalytic converter and ensure all bolts are tightened to the specified torque (usually around 30-35 lb-ft).
  4. Reconnect any exhaust hangers that were disconnected during removal.

4. Clear Error Codes

• After replacing components, reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's memory.