Coolant Light on, but coolant is full, and gauge is fine

[Bingus]

Hello, (2010 Corolla CE)

I'm hoping somebody can help me out with trouble shooting as I know the bare minimum about cars and this light is driving me crazy.

I have had my check engine light on for a while, it spits out a code for an O2 sensor. From my understanding at this point replacing that isnt dire (I may try to do it myself in summer, if the sensor isnt the case I'm probably looking at a new catalytic converter)

Recently my alternator was starting to go, there was an issue with my ABS system, and most recently my coolant light started coming on (It usually turns on immediately after turning the car on) I haven't actually tested the coolant (I do have a temp gun, just unsure of how I would use it. My gauge on my car does go up to a safe level consistently, just below the mid line when running, and doesn't seem to be acting sporadic)

Mechanic replaced my alternator, said there was a bad bearing,  my ABS system was a sensor slightly unplugged,  but they claimed my coolant light never went on for them.

Regardless, its still on for me and its driving me insane, I took the liberty of changing my temp sensor yesterday, but nothing is different.

From what I can see I don't see any leaks as my level has stayed full, and I don't hear anything wrong with my car.

Hoping somebody has dealt with a similar situation so I can start trouble shooting

[Obsidian Estate]

Does it have a level sensor on the reservoir?

Could it be that?

Or, has the Battery gotten a bit too  low from not being charged correctly and is throwing phantom errors?

[Bingus]

1 hour ago, Obsidian Estate said:

Does it have a level sensor on the reservoir?

Could it be that?

Or, has the battery gotten a bit too  low from not being charged correctly and is throwing phantom errors?

I just was reading about coolant level sensors online. But I can't seem to find anything online about it for 2010 corollas. 

I'm going to wait for my car to cool down and check again to see if I can find anything.

Just drove my car for 15 minutes and light wasn't on (but that had happened yesterday and light had turned back on at about 30 minutes)

 

I would say that my Battery was able to charge enough after all of the driving I had done yesterday with the new alternator. (I also replaced the Battery a couple years ago)

 

I guess it could just be a matter of wait and see.  Can he heat temp sensor  take a few cycles to be properly functioning?

[Derek.w]

Are you checking at the header tank or have you checked the radiator itself

fill it up using fluid in header tank.