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

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, infrared thermometer, socket set, torque wrench, and safety goggles.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before working on the exhaust system.

2. Replace Faulty O2 Sensors

1. Locate the O2 Sensors: Identify the upstream and downstream O2 sensors. The upstream sensor is located before the catalytic converter, and the downstream sensor is after it.
2. Remove the Old O2 Sensors:
   • Use a socket or wrench to unscrew the O2 sensors.
   • Carefully disconnect the electrical connectors.
3. Install New O2 Sensors:
   • Apply anti-seize compound to the threads of the new O2 sensors.
   • Install the upstream sensor first, followed by the downstream sensor.
   • Connect the electrical connectors to both sensors.
   • Torque the sensors to the manufacturer’s specifications (typically around 30 lb-ft).

3. Inspect and Replace Catalytic Converter (if necessary)

1. Assess Catalytic Converter Condition: If O2 sensor replacement does not resolve the issue, inspect the catalytic converter for internal damage or blockage.
2. Remove the Old Catalytic Converter:
   • Disconnect the exhaust pipes at the flanges using appropriate tools.
   • Remove any heat shields or mounting brackets.
   • Unbolt the catalytic converter from the exhaust system.
3. Install New Catalytic Converter:
   • Position the new catalytic converter in place.
   • Bolt it securely to the exhaust system, ensuring proper alignment.
   • Reattach any heat shields or brackets.
   • Torque bolts to manufacturer specifications.

4. Clear Codes and Test Drive

1. Reconnect Battery: Reconnect the negative battery terminal.
2. Clear the P0420 Code: Use the OBD-II scanner to erase the trouble codes.
3. Test Drive: Drive the vehicle for at least 20-30 minutes to allow the ECU to perform self-tests and check for the reappearance of the P0420 code.