help... Yesterday I drove my PT for almost 200 miles and it ran hot and we found out that the fan motor wasn't working so we changed it.. other than that NO PROBLEMS... its been parked ever since... I went to go to the store today and went i cranked it up the transmission light was on

... can anyone please tell me what could've happened or whats wrong... I drove it fine yesterday and the light never came on.. and its not been drove since.. then when i just cranked it today its on out of no where...