what does code P0420 indicate for my Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:

   • Tools required: O2 sensor socket, ratchet, and extension.
   • Disconnect the electrical connector and use the O2 sensor socket to unscrew the sensor from the exhaust manifold.

2. Install the new upstream oxygen sensor:

   • Apply anti-seize compound to the threads of the new sensor.
   • Screw it into the manifold and tighten to the manufacturer’s specifications (typically around 30-40 ft-lbs).
   • Reconnect the electrical connector.

3. Remove the downstream oxygen sensor (if needed):

   • Follow the same procedure as above to inspect or replace the downstream sensor.

3. Check and Replace the Catalytic Converter (if needed)

1. Inspect the catalytic converter:

   • Look for physical damage, rattling sounds, or excessive heat.

2. Remove the catalytic converter:

   • Tools required: Socket set and torque wrench.
   • Remove the bolts connecting the catalytic converter to the exhaust system and any heat shields.

3. Install the new catalytic converter:

   • Position the new converter in place, ensuring proper alignment.
   • Torque the bolts to the manufacturer’s specifications (usually around 30-35 ft-lbs).

4. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code and perform a drive cycle to monitor for any reoccurrence of the code.