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

Solution

1. Preparation

• Gather tools and parts needed.
• Disconnect the vehicle battery to ensure safety during repairs.

2. Inspect and Replace Oxygen Sensors

• Tools Needed: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream oxygen sensor:
  • Use the O2 sensor socket to unscrew the sensor from the exhaust manifold.
• Install a new upstream oxygen sensor:
  • Apply anti-seize lubricant to the new sensor threads.
  • Torque the sensor to the manufacturer's specification (typically around 30 lb-ft).
• Repeat the process for the downstream oxygen sensor if necessary.

3. Inspect and Replace Catalytic Converter

• Tools Needed: Socket set, jack and jack stands, exhaust pipe cutter.
• Raise the vehicle securely using a jack and jack stands.
• Remove the exhaust pipe connected to the catalytic converter:
  • Use the exhaust pipe cutter if needed to detach it from the rest of the exhaust system.
• Remove the catalytic converter:
  • Unscrew the bolts or nuts holding the converter in place.
• Install the new catalytic converter:
  • Position it correctly and secure it with new gaskets or seals.
  • Torque the bolts to the manufacturer’s specification.
• Reconnect the exhaust pipe.

4. Clear Error Codes

• Use the OBD-II scanner to clear the P0420 code from the engine control unit (ECU).
• Reconnect the vehicle battery.