how to fix P0420 code on Honda Accord 10th Generation (2018-2022)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a flat surface, and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter.
• Remove the upstream (pre-catalytic converter) oxygen sensor:
  1. Locate the sensor on the exhaust manifold.
  2. Use the O2 sensor socket to unscrew it from the exhaust.
  3. Check the connector for corrosion or damage.
  4. Install the new upstream O2 sensor and torque it to the manufacturer’s specifications (usually around 30 lb-ft).
• Repeat the process for the downstream (post-catalytic converter) oxygen sensor if necessary.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if needed).
• Remove the catalytic converter:
  1. Safely lift the vehicle using jacks and jack stands.
  2. Use the socket set to unbolt the catalytic converter from the exhaust pipes.
  3. Inspect the old catalytic converter for signs of damage or clogging.
  4. Install the new catalytic converter, ensuring all gaskets are replaced and bolts are torqued to specifications.

4. Check for Exhaust Leaks

• Inspect all joints and connections in the exhaust system, particularly around the catalytic converter and O2 sensors.
• Use exhaust leak detection spray or a soapy water solution to identify leaks.
• Repair any leaks with appropriate sealants or replace faulty sections of the exhaust pipe.

5. Reset the Engine Control Module (ECM)

• Reconnect the negative battery terminal.
• Start the vehicle and allow it to reach operating temperature.
• Use the OBD-II scanner to clear the P0420 code and monitor for any reoccurrence.