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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to avoid electrical shorts.
• Allow the vehicle to cool down before working on the exhaust system.

2. Inspect and Repair Exhaust Leaks

• Tools Required: Wrench set, exhaust sealant.
• Inspect all joints and connections in the exhaust system for leaks.
• If leaks are found, tighten connections or replace gaskets as necessary and apply exhaust sealant where needed.

3. Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, wrench set.
• Locate the upstream and downstream oxygen sensors in the exhaust manifold and catalytic converter.
• Disconnect the electrical connectors from both sensors.
• Remove the sensors using an O2 sensor socket.
• Install new oxygen sensors by threading them into place and tightening them to the manufacturer's torque specification (usually around 30 ft-lbs).
• Reconnect the electrical connectors.

4. Replace the Catalytic Converter (if necessary)

• Tools Required: Socket set, exhaust hanger removal tool.
• Disconnect the exhaust pipes from the catalytic converter by removing the bolts or clamps.
• Remove any exhaust hangers that support the catalytic converter using the exhaust hanger removal tool.
• Remove the old catalytic converter and install the new one, ensuring it is secured properly.
• Reconnect the exhaust pipes and tighten all bolts to the manufacturer's specifications.

5. Reset the Engine Control Module (ECM)

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0420 code from the ECM.