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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative terminal of the battery to prevent electrical shorts during repairs.

2. Inspect and Replace Oxygen Sensors

• Step 1: Identify the pre-catalytic and post-catalytic oxygen sensors (usually at the exhaust manifold and after the catalytic converter).
• Step 2: Use an O2 sensor socket to remove the sensors by turning counter-clockwise.
• Step 3: Inspect the wiring and connectors for damage; replace as necessary.
• Step 4: Install the new sensors by threading them in place and tightening them to the manufacturer's torque specifications (typically around 30-40 ft-lbs).

3. Inspect and Replace Catalytic Converter

• Step 1: If the catalytic converter is suspected to be faulty, loosen the bolts or clamps securing it to the exhaust system.
• Step 2: Carefully remove the old catalytic converter from the exhaust system.
• Step 3: Install the new catalytic converter, ensuring proper alignment with the exhaust pipes.
• Step 4: Tighten all bolts or clamps to the specified torque (usually around 30-40 ft-lbs).

4. Clear Error Codes

• Step 1: Reconnect the negative battery terminal.
• Step 2: Use the OBD-II scanner to clear the P0420 code.

5. Test Drive

• Step 1: Start the engine and allow it to reach operating temperature.
• Step 2: Take the vehicle for a test drive to ensure the check engine light does not return.