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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery before starting work on the vehicle.
• Allow the engine to cool down completely.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Using an O2 sensor socket, carefully remove the upstream oxygen sensor and inspect it for damage or contamination.
3. If the sensor is faulty, install a new oxygen sensor and torque it to the manufacturer's specifications (typically around 30 lb-ft).
4. Repeat the process for the downstream oxygen sensor if it’s also found to be defective.

3. Examine and Replace the Catalytic Converter

1. Inspect the catalytic converter for signs of physical damage or blockage.
2. If replacement is necessary, unbolt the catalytic converter from the exhaust manifold and the exhaust pipe using a socket set.
3. Replace with a new catalytic converter that meets OEM specifications.
4. Reinstall the catalytic converter and torque the bolts to the manufacturer's specifications (usually around 30-40 lb-ft).

4. Reset the Engine Control Module (ECM)

1. Reconnect the battery and start the engine.
2. Use the OBD-II scanner to clear the P0420 code from the ECM.
3. Allow the engine to run and monitor for any re-illumination of the check engine light.