how to troubleshoot P0420 code in Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors:

   • The upstream sensor is located before the catalytic converter, and the downstream sensor is after it.

2. Remove the Upstream Oxygen Sensor:

   • Use an oxygen sensor socket to unscrew the sensor from the exhaust pipe.
   • Disconnect the electrical connector from the sensor.

3. Install New Upstream Sensor:

   • Apply anti-seize compound to the threads of the new sensor.
   • Install and torque to manufacturer specifications (typically around 30-35 lb-ft).
   • Reconnect the electrical connector.

4. Repeat for the Downstream Oxygen Sensor:

   • Follow the same steps as above for the downstream sensor.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Check for Damage:

   • Inspect the catalytic converter for any signs of physical damage, such as dents or holes.

2. Remove the Catalytic Converter:

   • Remove any heat shields and exhaust hangers.
   • Unbolt the catalytic converter from the exhaust system (use a socket set).
   • Carefully lower the converter from the vehicle.

3. Install New Catalytic Converter:

   • Position the new catalytic converter in place.
   • Bolt it to the exhaust system, ensuring proper alignment.
   • Reinstall any heat shields and exhaust hangers.

4. Clear Codes and Test Drive

1. Reconnect the Battery:

   • Reconnect the negative battery terminal.

2. Clear the P0420 Code:

   • Use the OBD-II scanner to erase the trouble codes.

3. Test Drive the Vehicle:

   • Drive the vehicle for at least 15-20 minutes to allow the system to monitor the new components.