CEL tells a real code can be read....on top of P1624. This other code would..could...point to the actual trouble. I'd really like to se that code first. IN fact...in my interpretation, the transmission module works....since it can send the code to light up the CEL....
Look or ask for the actual transmission code...have Autozone read it for you is you cannot get your hands on a code reader...or buy a code reader..a 70$ to 100$ investment that pays for itself.