This morning on the way to school my check engine along with the traction control light came on. I noticed nothing in the way the truck handled, ran and drove fine. Any idea why it came on?

download the codes, then able to isolate. Could be the gas cap.

It is either the gas cap or the EVAP sensor on the drivers side of the engine.

Replace the gas cap first, they are about $25 dollars from Toyota (use the factory original one, not an aftermarket).

If its the EVAP sensor, they are about $145.

95% of the time, its the gas cap. Mine was.

every car owner should own a basic scan tool.
i recommend this bluetooth unit, plug it and leave it permanently on your obd port. download torque pro on googlr playstore and read off codes yourself. best $20 i have ever spent

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Thank you for posting this! Had no idea they have a blue tooth version. Unreal. Order placed!

Thank you all for the input. I do own a scan tool and it read "EVAP System Leak Detected (very small leak)"

Ill assume its the gas cap

Are you able to see live fuel trims? The Amazon page seems to indicate that it can.

I agree with this. I bought one of the higher end model scan tools that are offered at Harbor Freight which allows you to also clear the codes. I have been meaning to buy one of those ODB dongles though after reading about them on a Miata forum I belong to. They recommend using a WiFi version for people with iPhones though. I can’t remember which app they recommended for iOS users, but if I do, I’ll come back and update this. The nice thing about having the dongle and a phone app would be to take it with you when looking at used cars since it’s easily portable (fits in your pocket), so it won’t be so obvious to the seller/dealer that you are taking it for your test drive as it would with a full sized scan tool. I’ve known of many situations where people have cleared codes to sell cars, since many will not reappear with just a test drive. This way you can check for “pending codes”.

The app I use is "Auto Doctor"

Yep, I got a stant at auto store for $20.

Yes, it shows live data. stft, ltft o2 sensor voltages, CAT temps etc

This morning the lights went away on their own after installing the gas cap Friday

Purchased a 2019 sr5 a few months ago. 45k miles on it. The same lights came on for me. Autozone is saying its the cat converter. How is this so? I thought those things last close to 100k miles

Doubtful it's that but you need to share the actual code listed. I have over 200k on all but 1 cat on my 03.

BTW, you are in the wrong forum section for your year truck.

2019 is a gen 6- https://www.toyota-4runner.org/6th-gen-t4rs/

He has a 5th Gen not a 6th Gen, so he would get more people with advice in the 5th Gen forum.