Reading fault codes engine and transmission.

Hi there, I have a 91 Dynasty and pulling codes should be the same, you dont even have to jump the terminals, turn the key to the on position and then of then on then off then on again and leave it on, remember to do that 3 times, then watch the Check Engine Light, it will flash a 12 to let you know the computer is communicating and then any codes it may have stored then a 55 ending the reading, hope all goes well!