Ok so my vehicle never shifted into first gear, a couple of days ago I was messing with the auto manual and trying to shift down to first where magically for the first time in forever it shifted. However when I gave it gas it kinda moved but not really. Anyways ever since I’ve been having a problem where the car stalls out when I come to a stop. I recently changed out the radiator and fan assembly. Due to overheating. No more overheating problems but now I have this problem, I come to a complete stop and sometimes it will stall and turn off. At times as well while I’m driving the gear shows “E” and states to “Check transmission”. I turn off the car and turn it back on and it seems fine again. However when I shift Drive it turns off. Reverse and everything else seems fine. Could I be low on oil? Also I’m kinda overreving which never happened before. My gears are taking longer to pull. However it’s a sealed transmission. No leaks nada. So I’m clueless at this point. I was receiving codes referring to the Air idle control valve(electric) and I swapped it out. When I did the problem seemed to go away for about 15 minutes. Driving down the road I received the check transmission situation again where the gear indicates E. The car has about 231.456 miles. I’ve never had a problem with the car at all especially knowing it never shifted down to first I was ok with it because the car seemed to adapt to it and ran smoothly always. I just need to know is it the tranny going bad? Or do I need to get a new/refurbished IAC. I got one from a junkyard. Please help I am clueless and could someone please explain to me how you put oil in this transmission with pics if possible.