how to fix P0420 code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shock.
• Allow the engine to cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Disconnect the wiring harness from the sensors.
3. Remove the sensors using an oxygen sensor socket. Take care not to damage the threads.
4. Install new oxygen sensors:
   • Apply anti-seize compound to the threads of the new sensors.
   • Screw in the new sensors and tighten to manufacturer specifications (typically around 30 Nm).
5. Reconnect the wiring harness securely.

3. Inspect and Replace the Catalytic Converter (if needed)

1. Remove the exhaust manifold bolts connecting the catalytic converter to the exhaust system.
2. Unbolt the catalytic converter from the vehicle using a socket set.
3. Replace with a new catalytic converter:
   • Ensure the new converter is compatible with the Highlander XU70.
   • Install the new converter and torque bolts to manufacturer specifications (typically around 40 Nm).
4. Reconnect any exhaust hangers that were removed during the process.

4. Reset the Engine Control Module (ECM)

1. Reconnect the battery after all repairs are complete.
2. Use an OBD-II scanner to reset the check engine light and clear the P0420 code.