Check engine and check VSC system warning lights, code 0420

Hello,

The code P0420 is a Oxygen sensor code for your car.

DTC P0420 Catalyst System Efficiency Below Threshold (Bank 1)

That code should not trigger the VSC error.

https://www.2carpros.com/articles/how-an-oxygen-sensor-works
https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor

Here are some of the reason for that code:
Heated Oxygen (HO2S) Sensor 2
Heated Oxygen (HO2S) Sensor Bank 1 Sensor 2
Exhaust Front Pipe - Three Way Catalytic Converter (TWC) Rear Catalyst
Exhaust Manifold Converter Sub-Assembly - Three Way Catalytic Converter (TWC) Front Catalyst
Exhaust Manifold Sub-Assembly (Right) Three Way Catalytic Converter (TWC) Front Catalyst
Front Exhaust Pipe - Three Way Catalytic Converter (TWC) Rear Catalyst
Gas Leak From Exhaust System

I have attached the basic VSC error diagnostics for your reference.
VSC malfunction what triggered the traction control light.

Please keep in mind if the VSC needs to be programmed it will require special scanner.

Please let me know if you have any questions.

Thank you.

According to Toyota sometimes the engine light with the P0420 code it will trigger the VSC light and traction control light.
So the first step would be to get the engine light issue taken care off then clear the codes. Drive for few miles to see if it comes back on.

https://youtu.be/ahK_eucFi-k

Let me know if you have any questions.

Thank you.