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.
• Allow the vehicle to cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Locate the sensor on the exhaust manifold.
  2. Use the O2 sensor socket and ratchet to unscrew it.
• Install the new upstream oxygen sensor:
  1. Apply anti-seize compound to the threads of the new sensor.
  2. Hand-tighten it, then use the torque wrench to tighten it to manufacturer's specifications (usually around 30 ft-lbs).
• Repeat the process for the downstream (post-catalytic) oxygen sensor if required.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, exhaust hanger removal tool, torque wrench.
• Remove the catalytic converter:
  1. Loosen and remove the bolts connecting the catalytic converter to the exhaust manifold and the exhaust pipe.
  2. Use the exhaust hanger removal tool to detach the converter from the hangers.
• Install the new catalytic converter:
  1. Position the new converter and align it with the exhaust system.
  2. Hand-tighten the bolts, then use the torque wrench to tighten them to specifications (usually around 40-50 ft-lbs).
  3. Reattach any exhaust hangers.

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code and any other related codes.
• Start the engine and allow it to reach operating temperature.
• Take the vehicle for a test drive to ensure the check engine light does not reappear and monitor performance.