how to fix P0420 code on Honda Accord 9th Generation (2013-2017)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety.
• Allow the engine to cool before starting work.

2. Inspect and Replace Oxygen Sensors

• Inspect the upstream and downstream oxygen sensors.
  • Remove the connectors and inspect for corrosion or damage.
• Replace any faulty oxygen sensors.
  • Use a socket wrench to remove the sensor.
  • Apply anti-seize compound to the threads of the new sensor.
  • Install the new oxygen sensor, tightening it to the manufacturer's specification (usually around 30 Nm).

3. Check and Repair Exhaust Leaks

• Inspect the exhaust system for leaks.
  • Look for cracks in the exhaust manifold, pipe joints, or catalytic converter.
• Repair any leaks identified.
  • Use exhaust tape or replace damaged sections of the exhaust pipe.

4. Replace the Catalytic Converter (if necessary)

• If the catalytic converter is determined to be faulty, replace it.
  • Support the vehicle on jack stands.
  • Remove the bolts securing the catalytic converter using a socket wrench.
  • Disconnect any heat shields and oxygen sensor connectors.
  • Install the new catalytic converter in reverse order of removal, ensuring all bolts are torqued to manufacturer specifications (typically around 40-50 Nm).