Why does it shut down as soon as I put it in drive?

Prospective Owner: Sorry, that issue would require a diagnosis to determine the cause, a simple engine vacuum leak could be the culprit, or a major transmission problem could cause the same symptom, a good technician would connect a capable scan tool and look for trouble codes, analyze fuel trim, missfire counters, and a literal snap-shot of the parameters which exist at the time a code sets, called a " freeze frame". all of this information is available to the Technician so we can make an informed decision leading to an accurate diagnosis.

Hello, I am not that mechanically inclined but I have a similar issue, It started with my transmission slipping into neutral once in a great while, then it went to a stage where the transmission light would come on due to improper changing of gear. I could shut off the car then turn it back on , and would have no issues and if I eased the gas, the transmission would shift accordingly, its when I had to really step on it or accelerate I would begin to have issues. It got to the point where it would start, and idle but as soon as you raised the rpms it would die. In my research, Ive found it to be the TCM ( transmission Control Module) I found the part on ebay for about 50 dollars with shipping ( low price ) and its a 20 minute change. I hope this helped. My Car is also A 1997 Cadillac Catera.