how to fix P0420 code on my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather tools and safety equipment.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent any electrical issues during the repair.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:

   • Locate the upstream oxygen sensor (usually before the catalytic converter).
   • Use an oxygen sensor socket and ratchet to unscrew the sensor.

2. Install the new upstream oxygen sensor:

   • Apply anti-seize compound to the threads of the new sensor.
   • Screw in the new sensor by hand and then tighten it with the socket, ensuring not to overtighten (approximately 30 Nm / 22 lb-ft).

3. Repeat for the downstream oxygen sensor:

   • Locate and remove the downstream oxygen sensor using the same method.
   • Install the new sensor as described above.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove the exhaust manifold bolts:

   • Use a socket set to remove bolts securing the catalytic converter to the exhaust manifold.

2. Remove the catalytic converter:

   • Unbolt any additional brackets and disconnect the exhaust pipes attached to the catalytic converter.
   • Carefully remove the catalytic converter from its mounting.

3. Install the new catalytic converter:

   • Position the new catalytic converter in place and secure it with bolts.
   • Ensure all gaskets are replaced and connections are sealed properly.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code from the system.