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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative terminal of the battery to ensure safety.
• Raise the vehicle using jack stands and secure it on a level surface.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, wrench set, torque wrench, multimeter.
• Sub-steps:
  1. Remove the upstream and downstream oxygen sensors using the O2 sensor socket.
  2. Inspect the sensor connectors for corrosion or damage.
  3. Install new oxygen sensors, ensuring to torque them to manufacturer specifications (typically around 30 lb-ft).
  4. Reconnect the sensor connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, exhaust pipe cutter or saw, torque wrench, gasket scraper.
• Sub-steps:
  1. Inspect the catalytic converter for any physical damage or signs of overheating.
  2. Disconnect the exhaust pipes from the catalytic converter using a socket set.
  3. If replacement is needed, cut the old catalytic converter out using an exhaust pipe cutter or saw.
  4. Clean the mating surfaces with a gasket scraper to ensure a proper seal.
  5. Install the new catalytic converter and reconnect the exhaust pipes, torquing the bolts to manufacturer specifications (typically around 30 lb-ft).

4. Reset the Engine Control Module (ECM)

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Use the OBD-II scanner to clear the P0420 code from the ECM.
  2. Reconnect the negative battery terminal.