how to fix P0420 code on Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative terminal of the battery to ensure safety.
• Allow the exhaust system to cool before proceeding.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set
• Remove the upstream (pre-catalytic) oxygen sensor.
  • Disconnect the wiring harness.
  • Use an O2 sensor socket to unscrew the sensor from the exhaust manifold.
• Install the new oxygen sensor.
  • Apply anti-seize compound to the threads of the new sensor.
  • Screw it in by hand, then tighten to the manufacturer’s specified torque (usually 30 lb-ft).
• Repeat these steps for the downstream (post-catalytic) oxygen sensor if necessary.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if necessary)
• Raise the vehicle using a jack and secure it with jack stands.
• Locate and inspect the catalytic converter for damage or clogging.
• Remove the catalytic converter from the exhaust system.
  • Disconnect any brackets or bolts securing it.
  • Cut exhaust pipes if necessary.
• Install the new catalytic converter.
  • Ensure proper alignment with exhaust pipes and secure with bolts.
  • Reconnect any necessary sensors or brackets.

4. Reconnect Battery and Clear Codes

• Reconnect the negative terminal of the battery.
• Use the OBD-II scanner to clear the P0420 code and reset the check engine light.