YOUNGMU

ok my car sat in my backyard for 2months when i was away, when i got back i drove it and 50 miles later the tranny started to acttin funny, then now it wont shift but i can still drive it but i dont wanna drive in high rpms, it doesnt wanna shift, and when i gas the pedal it doesn't wanna accelerate at all so it takes about a minute to get to 40mph. i noticed that i have a leak that leaks out transmission fluid, here are the codes, po455, po730, po156, is my transmission bad?? how do i reset the limp mode will be helpful, i have an ml430, year 1999, thanks!!!

sosh

Sounds to me as if you have neglected maintenence on this ML. Get professional help from someone with repair experience and the correct eqipment to diagnose and repair. Yes you can do expensive damage by running the trans low on fluid which is a possibility if you have the leak you are talking about.