how to fix a P0420 code on my Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, multimeter, torque wrench, safety glasses, gloves.
• Safety Warnings: Disconnect the battery before working on electrical systems and allow the engine to cool before servicing exhaust components.

2. Inspect and Replace Oxygen Sensors

• Step 1: Use the OBD-II scanner to check the operation of the upstream and downstream oxygen sensors.
• Step 2: If a faulty sensor is detected, remove the sensor using a socket wrench.
• Step 3: Install the new oxygen sensor, ensuring to torque it to the manufacturer's specifications.
• Step 4: Reconnect the electrical connector to the new sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

• Step 1: If the oxygen sensors are functioning properly, inspect the catalytic converter for physical damage or clogging.
• Step 2: If replacement is needed, support the vehicle on jack stands and remove the exhaust components as necessary to access the catalytic converter.
• Step 3: Detach the catalytic converter from the exhaust system by removing the bolts with a socket wrench.
• Step 4: Install the new catalytic converter, ensuring all gaskets are in place and tightening bolts to the manufacturer's torque specifications.

4. Clear Codes and Test Drive

• Step 1: Reconnect the battery and use the OBD-II scanner to clear the P0420 code.
• Step 2: Start the engine and allow it to reach operating temperature.
• Step 3: Take the vehicle for a test drive to ensure the check engine light does not reappear and monitor the performance.