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

Solution

1. Preparation

• Gather tools and parts: OBD-II scanner, multimeter, socket set, torque wrench, oxygen sensor socket, replacement catalytic converter (if needed).
• Disconnect the vehicle battery to ensure safety during repairs.

2. Inspect Oxygen Sensors

• a. Remove the upstream oxygen sensor: Use an oxygen sensor socket and carefully unscrew it from the exhaust manifold.
• b. Check sensor condition: Inspect for carbon buildup or damage. Replace if necessary.
• c. Repeat for downstream oxygen sensor: Remove and inspect as above.

3. Inspect Catalytic Converter

• a. Remove exhaust components if necessary: Depending on the configuration, you may need to remove parts of the exhaust system.
• b. Visually inspect the catalytic converter: Look for physical damage, signs of overheating, or rattling sounds indicating internal failure.
• c. Perform a backpressure test: Connect a pressure gauge to the exhaust system to check for excessive backpressure, indicating a clogged converter.

4. Replace Catalytic Converter (if necessary)

• a. Remove the old catalytic converter: Use the socket set to unbolt the converter from the exhaust system.
• b. Install the new catalytic converter: Position the new component and secure with bolts to the manufacturer's specifications (typically around 25-30 ft-lbs).
• c. Reconnect exhaust components: Ensure all connections are tight and free of leaks.

5. Reinstall Oxygen Sensors

• a. Install the new or inspected oxygen sensors: Thread the sensors into their respective locations and torque to specifications (usually around 30 ft-lbs).
• b. Reconnect the vehicle battery: Ensure all connections are secure before reconnecting.