Hello guys I need some help about my 06 Corolla S, first of all I got this car from a private dealership with 170k miles for $4500.  I got it as an emergency because I lost my job due to COVID-19 and I was in need of a reliable vehicle.

The dealership provided me the Carfax info and everything about the vehicle. I can't complain, the vehicle is well maintained and has no issues. I've only invested on regular oil change and lately sparkplugs, that's it.

Few months ago a got a check engine light on, checked with my scanner and it gave me a code P0174 If I'm not wrong, which says the the transmission solenoid stuck off or something like that. 

I googled it and I found out that this especific year and model had that issue, one of the forums said that another person had the same problem but he didn't had any transmission problem or shifting, and that the code disappear itself after the third day. And the recommendation was to change the transmission oil.

So, same thing happened to me , after the 3rd day the check engine light turned off by itself and I also didn't had any trouble with the transmission shifting gears or anything.

But after this long explanation guys my question is if:

1)should just drain the oil and refill it?

2) should drain oil and replace filter?

3) do a transmission flush?

Like I said guys I don't have any problem with the transmission, the car is very very reliable, and I just want to hear about what you guys think I should do.