I have a light in the dash that looks like this (!)with a line underneath. It's beside the engine temperature

It may be the Engine Check Light.

https://www.jpauleytoyota.com/blog/what-are-toyota-dashboard-warning-lights-and-what-do-they-mean/

Aha, Catalytic converter Issue. Warning Symbol 29.

https://www.driven.co.nz/advice/advice/complete-guide-to-the-64-warning-lights-on-your-dashboard/

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Year make model engine size?

Hello! A thermometer light with two wavy lines underneath the thermometer indicates a problem with the VW's cooling system...When the engine is cold; Check the coolant level in the radiator...If it is full and since the light goes out when the engine reaches normal operating temperature the Low Coolant Level sensor is defective...But I suspect the level is low..
Guru...............saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

Visit the on-line store, known as reliable-store, they have the repair manuals. I'm sure you will get the solution of your problem.
2006 Kia Rio

check you radiator fluid it is low

Have you checked the engine coolant reservoir under the engine compartment.

If it looks like a deflating tire with an exclamation mark inside, its the check your tire pressure light.

If its a triangle with exclamation mark inside its the check engine light.

The one charging port is at the front of the engine compartment, look around the top right side of the radiator. The other one is at the back of the AC compressor, and can be found from underneath by removing the small splash shield in the front of the drivers side wheelwell.

wavy lines usullay means ckeck coolant level.

that means warning for driver so u should check mobile oil as well as engine problem