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

Solution

1. Preparation

• Gather 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, ratchet, torque wrench, multimeter
• Remove the upstream (pre-catalytic) oxygen sensor:
  • Locate the sensor in the exhaust manifold.
  • Use the O2 sensor socket to unscrew it.
• Install the new oxygen sensor:
  • Apply anti-seize compound to the threads of the new sensor (if applicable).
  • Install and torque to manufacturer's specifications (usually around 30-40 lb-ft).
• Repeat the process for the downstream (post-catalytic) oxygen sensor if needed.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, jack stands, exhaust pipe cutter, gaskets
• Lift the vehicle securely on jack stands.
• Disconnect the exhaust system from the catalytic converter:
  • Use an exhaust pipe cutter or saw to separate the connection if necessary.
• Remove the catalytic converter:
  • Unbolt the mounting brackets and any hangers holding the converter in place.
• Install the new catalytic converter:
  • Position it correctly and bolt it in place, ensuring all gaskets are new and properly seated.
  • Torque bolts to manufacturer's specifications.

4. Final Checks

• Reconnect the negative battery terminal.
• Clear the codes using an OBD-II scanner.