how to fix P0420 code on Honda Accord 8th Generation (2008-2012)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Remove the Pre-Catalytic Sensor:
   • Locate the pre-catalytic oxygen sensor.
   • Use an oxygen sensor socket to unscrew and remove the sensor.
   • Inspect the sensor for contamination and corrosion.
2. Install New Sensor:
   • Apply anti-seize compound to the threads of the new oxygen sensor.
   • Install the new sensor and tighten it to the manufacturer's specifications (usually around 30 Nm).
3. Repeat for Post-Catalytic Sensor:
   • Follow the same steps to remove and replace the post-catalytic oxygen sensor.

3. Replace Catalytic Converter (if necessary)

1. Remove Exhaust Components:
   • Unbolt the exhaust pipe from the catalytic converter using a socket set.
   • Disconnect any heat shields or brackets holding the catalytic converter.
2. Install New Catalytic Converter:
   • Position the new catalytic converter in place and secure it using new gaskets and bolts.
   • Torque the bolts to the manufacturer's specifications (refer to service manual for exact value).
3. Reconnect Exhaust Components:
   • Reconnect the exhaust pipe and any other components removed during the process.

4. Clear Codes and Test

1. Reconnect Battery:
   • Reconnect the negative battery terminal.
2. Clear Codes:
   • Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
3. Test Drive:
   • Take the vehicle for a test drive to ensure the check engine light does not reappear and that performance is restored.