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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is on a level surface and securely raised with jack stands.
• Disconnect the negative terminal of the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Remove Oxygen Sensors:
   • Use an oxygen sensor socket to carefully unscrew the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
   • Disconnect the wiring harness from both sensors.
2. Install New Oxygen Sensors:
   • Apply anti-seize compound to the threads of the new sensors.
   • Install the new sensors by hand and then tighten to the manufacturer’s specified torque (usually around 30 ft-lbs, but verify in the service manual).

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove Exhaust Components:
   • Unbolt and remove any exhaust hangers that may obstruct access to the catalytic converter.
   • Use a socket set to remove the bolts connecting the catalytic converter to the exhaust manifold and exhaust pipe.
2. Install New Catalytic Converter:
   • Position the new catalytic converter and secure it with new gaskets and bolts as per the manufacturer’s specifications (torque to around 30 ft-lbs).
   • Reattach all exhaust hangers and ensure there are no leaks.

4. Reconnect Battery and Test

• Reconnect the negative battery terminal.
• Start the engine and allow it to reach operating temperature.
• Clear the P0420 code using the OBD-II scanner and monitor for any reoccurrence.