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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative terminal of the battery to ensure safety.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:
   • Use an oxygen sensor socket to unscrew the sensor from the exhaust manifold.
   • Disconnect the wiring harness.
2. Install the new upstream oxygen sensor:
   • Apply anti-seize compound to the threads of the new sensor.
   • Tighten to the manufacturer’s specification (usually around 30 Nm or 22 lb-ft).
   • Reconnect the wiring harness.
3. Repeat for the downstream oxygen sensor if necessary, following the same steps.

3. Inspect and Replace Catalytic Converter (if needed)

1. Remove the catalytic converter:
   • Unbolt the exhaust clamps and any heat shields that may obstruct access.
   • Use a socket set to detach the catalytic converter from the exhaust pipes.
2. Install the new catalytic converter:
   • Position the new converter and secure it with bolts, ensuring proper alignment.
   • Torque the bolts to the specified value (usually around 40 Nm or 30 lb-ft).
3. Reinstall any heat shields or exhaust clamps removed earlier.

4. Final Checks

• Reconnect the negative battery terminal.
• Start the engine and let it idle for a few minutes to check for leaks.
• Use the OBD-II scanner to clear the trouble codes and monitor for any reoccurrence.