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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical issues during repair.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, torque wrench.
• Remove the upstream oxygen sensor:
  1. Locate the upstream O2 sensor near the exhaust manifold.
  2. Use the O2 sensor socket to unscrew the sensor.
  3. Install the new upstream O2 sensor and torque it to manufacturer specifications (typically around 30-40 ft-lbs).
• Repeat for the downstream O2 sensor.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, exhaust pipe cutter, welding equipment (if applicable), gasket scraper.
• Locate the catalytic converter in the exhaust system.
• Remove the catalytic converter:
  1. Unbolt the mounting brackets and exhaust clamps securing the converter.
  2. Cut the exhaust pipes if necessary to remove the converter.
• Install the new catalytic converter:
  1. Position the new converter in place.
  2. Bolt it securely and replace any gaskets as needed.
  3. Ensure all connections are tight to prevent leaks.

4. Clear Error Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 error code from the vehicle's computer.