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

Solution

1. Preparation

• Gather the necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.

2. Inspect Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter, socket set.
• Remove the oxygen sensor from the exhaust manifold (pre-cat) using a socket.
• Test the sensor using a multimeter to ensure it is functioning correctly. Replace if faulty.

3. Examine the Catalytic Converter

• Tools Required: Wrench set, temperature probe.
• Inspect the catalytic converter for any physical damage, such as dents or rust.
• Use a temperature probe to measure the inlet and outlet temperatures of the catalytic converter. A difference of more than 100°F indicates a failing converter.

4. Replace Components if Necessary

• If the oxygen sensors or catalytic converter are found to be faulty:
  • Oxygen Sensor Replacement:
    • Install the new oxygen sensor in the exhaust manifold, tightening it to the manufacturer's specification (usually around 30 ft-lbs).
  • Catalytic Converter Replacement:
    • Remove the exhaust pipes connected to the catalytic converter.
    • Unbolt the catalytic converter from the exhaust manifold and remove it.
    • Install the new catalytic converter, ensuring all gaskets are in place and bolts are torqued to the manufacturer's specifications.

5. Reconnect Battery and Clear Codes

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.