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

Solution

1. Preparation

• Gather required tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Allow the vehicle to cool down if it has been running.

2. Inspect Exhaust System

• Sub-step 1: Visually inspect the exhaust manifold, pipes, and catalytic converter for any signs of leaks or damage.
• Sub-step 2: Use exhaust leak detection fluid or spray to identify leaks by applying it around joints and connections.
• Tools Required: Flashlight, exhaust leak detection fluid.

3. Replace Oxygen Sensors (if necessary)

• Sub-step 1: Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Sub-step 2: Disconnect the electrical connectors from the sensors.
• Sub-step 3: Use an O2 sensor socket or appropriate wrench to remove the old sensors.
• Sub-step 4: Install the new sensors, ensuring they are properly torqued (usually around 30 ft-lbs).
• Sub-step 5: Reconnect the electrical connectors.
• Tools Required: O2 sensor socket, torque wrench.

4. Replace or Clean Catalytic Converter

• Sub-step 1: If the catalytic converter is damaged or clogged, consider replacement. If cleaning is an option, use a catalytic converter cleaner according to the product instructions.
• Sub-step 2: Remove the catalytic converter from the exhaust system by unbolting it from the flanges.
• Sub-step 3: Clean the inlet and outlet ports if applicable, then reinstall the catalytic converter, ensuring proper alignment and torque specifications (typically around 40 ft-lbs).
• Tools Required: Socket set, torque wrench.

5. Clear Error Codes

• Sub-step 1: Reconnect the negative battery terminal.
• Sub-step 2: Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
• Sub-step 3: Perform a test drive to monitor if the code reappears.
• Tools Required: OBD-II scanner.