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

Solution

1. Preparation

• Gather necessary tools and parts before starting.
• Safety warning: Disconnect the negative battery cable to prevent electrical shock.
• Tools required: OBD-II scanner, socket set, torque wrench, multimeter, exhaust pipe cutter (if needed), and safety glasses.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream and downstream oxygen sensors.
   • The upstream O2 sensor is typically found before the catalytic converter, while the downstream O2 sensor is after it.
2. Remove the upstream O2 sensor.
   • Use an O2 sensor socket or a wrench to unscrew it.
3. Install the new upstream O2 sensor.
   • Apply anti-seize compound on the threads (if necessary) and torque to manufacturer specifications (usually around 30 lb-ft).
4. Repeat the same process for the downstream O2 sensor.

3. Inspect and Replace the Catalytic Converter

1. Check for exhaust leaks.
   • If leaks are found, repair them before replacing the catalytic converter.
2. Remove the catalytic converter.
   • Unbolt the exhaust flanges and use an exhaust pipe cutter if necessary. Ensure to support the exhaust system to prevent damage.
3. Install the new catalytic converter.
   • Align it properly and torque the bolts to the specified values (typically 25-30 lb-ft).
4. Reconnect any oxygen sensors and exhaust components that were disconnected.

4. Clear Codes and Test Drive

1. Reconnect the negative battery cable.
2. Use the OBD-II scanner to clear the P0420 code.
3. Perform a test drive to monitor vehicle performance.