Revving high at idle

[Nina]

Stuck!

I'm stumped! The coolant light on my 2008 Yaris LE Auto with over 200k was taking way too long after warming up for the light to go off on the dashboard to the point that the car could not go into overdrive on the highway because it's supposed to reach 55*C. Eventually, the light wasn't shutting off at all! So I changed the thermostat twice and tried three different engine coolant temperature sensors and replaced the coolant with fresh mixture. I hooked up my Torque OBD app and noticed it doesn't go higher than 40* C when warming up.

Now the car also revs at about 2000 rpm's in park but does come down to the normal 750 rpm zone but only when in drive and reverse but as soon as I put it in Park or Neutral, it revs high again. I cleaned the TB and replaced the MAF sensor and checked all hoses for a vacuum leak - nada. No change!!!

I though I'd spend on the small parts first but they are also adding up! I'm at a loss here...I cleared the ECM many times by unplugging the battery as that would have forced the car to re-learn its rpm's and taking it for a spin but the two problems continue.

Is the ECM toast? Everything else works like it should...