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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, exhaust backpressure gauge, safety glasses, gloves.
• Disconnect the battery to ensure safety while working on the vehicle.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream and downstream oxygen sensors.
2. Disconnect the electrical connectors from both sensors.
3. Use a socket wrench to remove the oxygen sensors from the exhaust system.
4. Install new oxygen sensors in reverse order, ensuring proper torque (generally 30-40 ft-lbs).
5. Reconnect the electrical connectors firmly.

3. Inspect and Replace the Catalytic Converter

1. Position the vehicle on a lift or jack stands for access.
2. Remove any heat shields or brackets securing the catalytic converter.
3. Disconnect the exhaust pipes from both ends of the catalytic converter using a socket set.
4. Remove the catalytic converter from the vehicle.
5. Install the new catalytic converter, ensuring proper alignment and sealing.
6. Reattach all bolts and brackets, tightening to manufacturer specifications (typically around 30-40 ft-lbs).
7. Reinstall any heat shields that were removed.

4. Reset the Engine Control Module (ECM)

1. Reconnect the battery terminals.
2. Use the OBD-II scanner to clear the P0420 code from the ECM.
3. Perform a drive cycle to allow the ECM to re-evaluate the catalytic converter efficiency.