Why does my 2022 Toyota Highlander display an error code P0420?

Error Code P0420 Diagnosis: 2022 Toyota Highlander

Symptom: The error code P0420 indicates "Catalyst System Efficiency Below Threshold (Bank 1)." This typically manifests as a check engine light on the dashboard, and you may notice a decrease in fuel economy or performance.

Repair Instructions

Step 1: Repair or Replace Components

1. O2 Sensor Replacement:

   • If the upstream O2 sensor is faulty, replace it:
     • Disconnect the sensor connector.
     • Use an O2 sensor socket to unscrew it from the exhaust.
     • Install the new sensor, torque to manufacturer specifications.
     • Reconnect the harness.

2. Catalytic Converter Replacement:

   • If the catalytic converter is found to be faulty:
     • Raise the vehicle securely on jack stands.
     • Remove any bolts or clamps securing the catalytic converter using appropriate sockets.
     • Carefully remove the converter from the exhaust system.
     • Install the new catalytic converter, ensuring all gaskets are replaced.
     • Torque the bolts to the manufacturer specifications.

Step 2: Clear Codes

• Using the OBD-II Scanner: After repairs, clear the error codes and any pending codes from the system.

Step 3: Test Drive

• Perform a Test Drive: Drive the vehicle for at least 20 minutes to allow the system to perform readiness tests. Monitor for reoccurrence of the check engine light.

Step 4: Re-scan the Vehicle

• Verify the Repair: After the test drive, re-scan the vehicle to ensure the P0420 code does not return.

Conclusion

If the error code P0420 persists after following these steps, it may indicate further issues with the engine's air-fuel mixture or additional exhaust system components. In such cases, consulting with a professional technician or the dealership is recommended for a more in-depth diagnosis.