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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Find the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Remove the upstream oxygen sensor:
   • Use an oxygen sensor socket to unscrew the sensor from the exhaust manifold.
   • Inspect the sensor for contamination or damage.
3. Install the new upstream oxygen sensor:
   • Apply anti-seize compound on the threads (if not pre-applied).
   • Torque the sensor to the manufacturer's specification (usually around 30 lb-ft).
4. Repeat the above steps for the downstream sensor if it is also defective.

3. Inspect and Replace the Catalytic Converter

1. Check the catalytic converter condition:
   • Look for physical damage or signs of overheating (discoloration).
2. Remove the catalytic converter:
   • Unbolt the exhaust flanges using a socket set.
   • Disconnect any heat shields or brackets securing it.
3. Install the new catalytic converter:
   • Position the new catalytic converter and secure it with the bolts.
   • Torque the bolts to the manufacturer's specifications (usually around 25-30 lb-ft).

4. Clear the Codes

1. Reconnect the battery.
2. Use an OBD-II scanner to clear the P0420 code from the ECM.

5. Test Drive the Vehicle

• Drive the vehicle for a short distance to allow the ECM to re-evaluate the sensor readings and confirm the repair.