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

Solution

1. Preparation

• Gather tools and parts: OBD-II scanner, multimeter, socket set, torque wrench, replacement O2 sensors (if needed), and a new catalytic converter (if needed).
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Inspect and Replace O2 Sensors (if needed)

1. Disconnect Battery

   • Disconnect the negative battery terminal to prevent electrical shorts.

2. Remove O2 Sensors

   • Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) O2 sensors.
   • Use a socket or O2 sensor wrench to unscrew the sensors from their respective locations.

3. Install New O2 Sensors

   • Apply anti-seize compound to the threads of the new O2 sensors.
   • Screw the new sensors into their respective locations and tighten to the manufacturer’s specifications (usually around 30 Nm or 22 lb-ft).
   • Reconnect the electrical connectors for each sensor.

3. Inspect and Replace Catalytic Converter (if needed)

1. Remove Exhaust Components

   • If the catalytic converter is faulty, you may need to remove additional exhaust components. Use a socket set to remove any bolts securing the converter.

2. Remove Catalytic Converter

   • Carefully unbolt the catalytic converter from the exhaust manifold and the exhaust pipe. Use penetrating oil if necessary to loosen any rusted bolts.
   • Remove the converter from the vehicle.

3. 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 (typically around 40-60 Nm or 30-44 lb-ft).

4. Reconnect Battery and Clear Codes

1. Reconnect Battery

   • Reconnect the negative battery terminal.

2. Clear Error Codes

   • Use the OBD-II scanner to clear the P0420 code and any other stored codes.