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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to avoid electrical shorts.
• Raise the vehicle on jack stands for better access to the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Use an O2 sensor socket to remove the sensors from the exhaust manifold and catalytic converter.
  3. Inspect the sensors for damage or contamination.
  4. Install new oxygen sensors, ensuring to apply anti-seize compound on the threads.
  5. Torque the sensors to the manufacturer’s specified value, usually around 30 Nm (22 lb-ft).

3. Check and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. Inspect the catalytic converter for physical damage or clogging.
  2. If replacement is necessary, unbolt the catalytic converter from the exhaust system using a socket set.
  3. Remove any heat shields and gaskets to access the converter fully.
  4. Install the new catalytic converter, ensuring proper alignment and sealing.
  5. Torque the bolts to the manufacturer's specifications, typically around 40 Nm (30 lb-ft).

4. Reconnect Battery and Clear Codes

• Sub-steps:
  1. Reconnect the battery terminals, ensuring they are secure.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer system.

5. Road Test

• Sub-steps:
  1. Start the engine and allow it to reach operating temperature.
  2. Monitor engine performance and check for any warning lights.
  3. Perform a test drive, observing for any symptoms or recurrence of the check engine light.

Tools Required:

• OBD-II scanner
• Oxygen sensor socket
• Socket set
• Torque wrench
• Digital thermometer
• Jack and jack stands

Parts Required:

• Upstream oxygen sensor
• Downstream oxygen sensor
• Catalytic converter (if needed)
• Exhaust gaskets

Estimated Repair Time: 2-4 hours

Safety Warnings:

• Disconnect the battery before working on electrical systems to avoid shocks or shorts.
• Allow the engine to cool before working on the exhaust system to prevent burns.