96 gt problems

Well i have been driving another car the past week. Ive started and drove my car once and tried again today and the battery was completely dead. So i jumped it and was on my way, started driving down the street and noticed my speedo wasnt working, theft light was flashing, o/d off light flashing and my check engine light came on. What could have happened? its not like anyone else was driving the car and not like anything could have gotten messed up. I have no clue what to look for so i just disconnected my battery to restart the system.mn

well i just plugged the battery back in since i just got back home and i just backed out a little and spun my tires to see if the speedo moved and it did a little so i gotta take it back out agian and down the road and see if thats working and all the other lights are off except the theft light which still flashes at me.

Well drove it and i started watching the theft light and i noticed it would flash 6 times, pause and flash 1 time and just kept doing that. I know when my airbag light would do that it was a code so im guessing with the theft system its the same thing? so code 61 or 16 depending on how you look at it.