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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Raise the vehicle using a jack and secure with jack stands.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench.
• Remove the upstream (pre-catalytic) O2 sensor:
  1. Locate the upstream O2 sensor on the exhaust manifold or near the catalytic converter.
  2. Use the O2 sensor socket to unscrew and remove the sensor.
  3. Install the new O2 sensor, tightening to the manufacturer's specified torque (usually around 30 lb-ft).
• Repeat the process for the downstream (post-catalytic) O2 sensor if necessary.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary).
• Remove the catalytic converter:
  1. Locate the catalytic converter and disconnect any heat shields.
  2. Unscrew the bolts or nuts securing the converter to the exhaust manifold and the exhaust pipe.
  3. Remove the catalytic converter from the exhaust system.
• Install the new catalytic converter:
  1. Position the new catalytic converter in place, aligning it with the exhaust manifold and exhaust pipe.
  2. Secure it with new gaskets and bolts, tightening to the specified torque (usually between 25-30 lb-ft).

4. Reconnect Battery and Clear Codes

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