how to troubleshoot P0420 code on Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, socket set, torque wrench, temperature probe.
• Ensure the vehicle is parked on a flat surface and the engine is cool.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Disconnect the negative battery terminal.
  2. Use the OBD-II scanner to identify which oxygen sensor may be faulty (if applicable).
  3. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  4. Disconnect the electrical connectors from both sensors.
  5. Remove the sensors using a socket wrench.
  6. Install new oxygen sensors, ensuring they are torqued to the manufacturer's specifications (typically 30-40 lb-ft).
  7. Reconnect the electrical connectors.

3. Examine and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. If the catalytic converter is confirmed faulty, raise the vehicle and secure it on jack stands.
  2. Detach the exhaust pipes connected to the catalytic converter using a socket wrench.
  3. Remove any mounting brackets or bolts securing the catalytic converter.
  4. Carefully take out the old catalytic converter.
  5. Install the new catalytic converter, ensuring all bolts are tightened to the manufacturer's torque specifications.
  6. Reconnect the exhaust pipes and brackets.

4. Clear Codes and Test Drive

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Start the engine and let it idle for a few minutes.
  4. Take the vehicle for a test drive to ensure the check engine light does not reappear.