how to fix Toyota Highlander Fourth Generation (2020-present) P0420 code

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, exhaust pressure gauge, safety glasses, gloves.
• Clear the P0420 code using the OBD-II scanner after completing the diagnostic steps.

2. Inspect and Replace Catalytic Converter

1. Lift the Vehicle:

   • Use jack stands to securely lift and support the vehicle.
   • Ensure the vehicle is stable before working underneath.

2. Remove Exhaust Components:

   • Using a socket set, disconnect the exhaust pipes connected to the catalytic converter.
   • If applicable, detach any heat shields protecting the catalytic converter.

3. Inspect the Catalytic Converter:

   • Examine the converter for physical damage or external leaks. If it's clogged or damaged, proceed to replace it.

4. Replace Catalytic Converter:

   • Install the new catalytic converter by aligning it with the exhaust pipes.
   • Use a torque wrench to tighten the bolts to the manufacturer's specifications (consult repair manual for torque settings).

3. Inspect and Replace Oxygen Sensors (if necessary)

1. Locate Oxygen Sensors:

   • Identify and locate the upstream (pre-cat) and downstream (post-cat) oxygen sensors.

2. Test Oxygen Sensors:

   • Use a multimeter to check the voltage output of each oxygen sensor while the engine is running. Replace any sensor that does not meet specifications.

3. Install New Oxygen Sensors:

   • If replacement is necessary, apply anti-seize compound to the threads of the new sensors and install them. Tighten to the manufacturer's specifications.

4. Final Checks

• Reconnect any exhaust components and heat shields removed during the process.
• Lower the vehicle and start the engine to check for leaks and ensure everything is functioning properly.