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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the vehicle battery to ensure safety while working on electrical components.
• Raise the vehicle safely on jack stands if necessary to access the exhaust system.

2. Oxygen Sensor Replacement

• Tools Required: O2 sensor socket, wrench set, penetrating oil (if necessary).
• Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Apply penetrating oil to the threads of the oxygen sensors if they are rusted.
• Use the O2 sensor socket to remove the upstream sensor first. Disconnect the wiring harness.
• Install the new upstream oxygen sensor:
  • Apply anti-seize compound to the threads (if required).
  • Tighten to the manufacturer's specifications (usually around 30 lb-ft).
• Repeat the process for the downstream oxygen sensor.

3. Catalytic Converter Inspection/Replacement

• Tools Required: Socket set, torque wrench, exhaust gasket, and possibly new exhaust clamps.
• Inspect the catalytic converter for physical damage or clogging.
• If replacement is necessary, disconnect the exhaust hangers and any mounting bolts.
• Remove the old catalytic converter and clean the exhaust flanges.
• Install the new catalytic converter:
  • Position the new unit and ensure it aligns properly with the exhaust.
  • Secure it using new gaskets and bolts, torqued to specifications (typically around 30 lb-ft).
• Reattach any hangers or brackets that were removed.