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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• 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

• Tools Required: O2 sensor socket, wrench set, torque wrench, penetrating oil.
• Instructions:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Apply penetrating oil to the base of the sensors and allow it to soak for a few minutes.
  3. Disconnect the electrical connectors from both sensors.
  4. Use the O2 sensor socket to remove the sensors from the exhaust pipe.
  5. Install the new sensors by threading them in by hand, then tightening to the manufacturer’s torque specification (usually around 30 ft-lbs).
  6. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust gasket, jack stands.
• Instructions:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Locate the catalytic converter in the exhaust system.
  3. Unbolt the exhaust pipes connected to the catalytic converter using the socket set.
  4. Remove the old catalytic converter and inspect the exhaust system for any other issues.
  5. Install the new catalytic converter using a new exhaust gasket.
  6. Torque the bolts to the manufacturer's specifications (typically around 40 ft-lbs).
  7. Lower the vehicle back to the ground.

4. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear any trouble codes from the vehicle's computer.
• Start the engine and ensure there are no leaks in the exhaust system.