factory or aftermarket

Yes, Try dis-connecting the battery for a few minutes and see what happens. You may have to have it taken to, or buy and OBD II scanner that will clear codes to get it to release the immobilizer.

I have a similar problem. Factory system. 1997 626. Remote is long gone. Just had to change battery. The alarm system comes on and prevents starting the car. I wasn't there but the guy who changed it tried the instructions in manual to disarm the system to no avail.

Is it possible to simply remove a fuse, etc., to disable the alarm system or do I need to call dealership? I thought I may try to purchase an aftermarket remote but I don't know if I will be able to sync it with the factory alarm system until I've successfully started the car.

Any advice would be greatly appreciated!