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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Ensure the vehicle is on a level surface and secure it with jack stands if needed.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) sensors.
2. Remove the oxygen sensors:
   • Use an oxygen sensor socket.
   • Disconnect the wiring harness from each sensor.
3. Install new oxygen sensors:
   • Apply anti-seize compound to the threads of the new sensors (if not pre-applied).
   • Hand-tighten them, then use the oxygen sensor socket to torque them to the manufacturer's specification (usually around 30 lb-ft).
   • Reconnect the wiring harness.

3. Examine and Replace the Catalytic Converter (if necessary)

1. Remove the exhaust components:
   • Loosen the clamps or bolts securing the catalytic converter to the exhaust system.
   • Remove any heat shields if applicable.
2. Install the new catalytic converter:
   • Position the new catalytic converter in place.
   • Secure it with new gaskets and torque the bolts to the manufacturer's specifications.
   • Reinstall heat shields if removed.

4. Clear the Codes

• Reconnect the battery.
• Use the OBD-II scanner to clear any diagnostic trouble codes (DTCs) from the vehicle’s computer.