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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.

2. Inspect and Replace Oxygen Sensors

• Remove the upstream oxygen sensor using an O2 sensor socket.
• Inspect for carbon buildup; if present, clean or replace the sensor.
• Install the new or cleaned oxygen sensor and torque to manufacturer specifications (typically around 30 ft-lbs).
• Repeat for the downstream oxygen sensor if necessary.

3. Inspect Exhaust System

• Visually inspect the exhaust system from the manifold to the catalytic converter for any signs of leaks or damage.
• If leaks are found, repair or replace damaged sections using appropriate exhaust sealants or components.

4. Clean or Replace Catalytic Converter

• If the catalytic converter is clogged or damaged, it may need cleaning or replacement:
  • For cleaning: Use a catalytic converter cleaner according to the product instructions.
  • For replacement:
    • Remove the catalytic converter by unbolting it from the exhaust system.
    • Install the new catalytic converter using new gaskets and torquing bolts to specifications (usually around 25-30 ft-lbs).

5. Reset Check Engine Light

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code and reset the check engine light.