2004 Grand AM GT Remote Start

it could be passlock failing if they used a module it could be bad or if they used resistors to do passlock the value could have been close enough to start at first but over time reisistors change slightly and it may not be close enough to start sometimes. Passlock can be funy like that ive seen vehicles that are close enogh to the value to start yet far away enoght to trip the security light. One thing to check is when you start it up and it dies What is the security light doing if its flashing that probably it.

Try putting the key in the Ignition but don't turn it on. Now try remote starting leaving the key alone. If it starts and remains running then you probably have a problem with your security bypass. If it starts successfully a few times...take the key back out and retry the remote start. If it fails again then you definitely have something wrong with the bypass. PS. If your having a problem recreating the problem whenever it goes back to the shop...I would try pulling out a camcorder and recording it then taking it in and showing them what you keep experiencing.