what does it mean when my Toyota Highlander has a P0420 code

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is on a level surface and engage the parking brake.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Sub-steps:
  1. Disconnect the battery to prevent any electrical shorts.
  2. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  3. Use an oxygen sensor socket to remove the upstream oxygen sensor.
  4. Install the new oxygen sensor and tighten to manufacturer's torque specification (usually around 30-40 lb-ft).
  5. Repeat for the downstream sensor if it is also faulty.
• Tools Required: Oxygen sensor socket, torque wrench, multimeter.

3. Examine and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. If the catalytic converter is damaged or clogged, disconnect the exhaust pipes using a socket set.
  2. Remove any mounting hardware holding the catalytic converter in place.
  3. Install the new catalytic converter, ensuring proper alignment with exhaust pipes.
  4. Tighten all bolts to the manufacturer's torque specifications.
• Tools Required: Socket set, torque wrench, exhaust hanger removal tool.

4. Clear Codes and Test Drive

• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the ECM.
  3. Perform a test drive to ensure the issue is resolved and the check engine light does not reappear.
• Tools Required: OBD-II scanner.