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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Lift the vehicle using jack stands for better access to the exhaust system.

2. Inspect and Repair Exhaust System

• Visual Inspection: Examine all joints, clamps, and the exhaust pipe for leaks or damage.
• Repair Leaks: Use exhaust sealant or replace damaged sections of the exhaust if leaks are found.

3. Test and Replace Oxygen Sensors

• Remove Oxygen Sensors: Use an O2 sensor socket to remove the upstream and downstream sensors.
• Test Sensors: Connect the multimeter to check the sensor voltages.
  • Upstream sensor should fluctuate between 0.1V and 0.9V.
  • Downstream sensor should be stable if the catalytic converter is functioning properly.
• Replace Faulty Sensors: Install new sensors if any are malfunctioning. Torque to manufacturer specifications (usually around 30 lb-ft).

4. Replace Catalytic Converter (if necessary)

• Remove the Old Converter: Unbolt the catalytic converter from the exhaust system using a socket set.
• Install New Converter: Position the new catalytic converter in place and secure it using new gaskets and bolts. Torque to manufacturer specifications (typically around 30 lb-ft).
• Reconnect Oxygen Sensors: Reinstall the oxygen sensors on the new catalytic converter.

5. Final Steps

• Reconnect Battery: Reconnect the negative terminal of the battery.
• Clear Codes: Use the OBD-II scanner to clear the P0420 code.
• Test Drive: Monitor for any recurring codes after a test drive.