why does my Honda Accord Eleventh Generation (2023-present) have a check engine light with P0420 cod...

Solution

1. Preparation

• Gather necessary tools and parts.
• Park the vehicle on a level surface and engage the parking brake.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter
• Sub-steps:
  1. Reconnect the battery and start the engine.
  2. Use the OBD-II scanner to monitor live data from the oxygen sensors.
  3. Check the voltage readings: the upstream sensor should fluctuate between 0.1V to 0.9V, while the downstream sensor should generally remain stable around 0.5V.
  4. If the upstream sensor is faulty, replace it.

3. Inspect and Test the Catalytic Converter

• Tools Required: Exhaust gas analyzer (optional), basic hand tools
• Sub-steps:
  1. Inspect the catalytic converter for any physical damage, cracks, or signs of overheating.
  2. If equipped, use an exhaust gas analyzer to measure the efficiency of the catalytic converter.
  3. If the catalytic converter is found to be defective, proceed to replace it.

4. Replace Damaged Components

• Tools Required: Socket set, torque wrench, gasket scraper
• Sub-steps:
  1. If replacing the catalytic converter, remove the exhaust system components connected to it.
  2. Carefully unbolt the catalytic converter, ensuring not to damage any surrounding components.
  3. Install the new catalytic converter and ensure all bolts are torqued to manufacturer specifications.
  4. Reinstall any removed exhaust components.