Car security lock out after car is started

The keyless entry is broken hasent worked for a while the car opens with the key the engine starts and the lights all over the car starts to flash and the security light flashes when the lights go out the car is running still sometimes the trannie is locked in park I have to disconect the battery to get the car to reset that works sometimes I have herd that pulling the fuse on the security system stops the problem where is this problem

I am have the same issue with a customers 2002 saturn L100, she brought it in and the interior lights were flashing on and off when the door was open, also the headlights were flashing on and off at the same time, but only when the headlight switch was in the auto position and the running lights are on, when the headlights are put on manually from the switch they dont flash only the running lights do, also after about 5-10 seconds the temperature and fuel gauge fall to off, if I turn thr key on and off they work again and after 5-10 seconds they turn off again. Also since the first day I was checking the vehicle the interior and running lights no longer act up consistantly, its intermitant and spiratic. I have 3 communication codes in my bcm 1088, 1016, 1096 all of which are communication codes, 1016 is the first to show up, fallowed by 1096, and then 1088 with come a minute later

Yes I can read codes and communicate with the bcm, I have a used one on order should get it tomorrow and we will take it from there. Although all my data line show continuity, I believe the bcm must be eating some of it, once the codes are reset the cluster works again and then shuts down after 5 seconds

Yes I am aware of all that thanks for the info though I appreciate it, will let you know how it works out, cheers