There's no computer in the sense of a central processing unit (CPU) and motherboard like you'd find in a modern car in a 1991 Ford Econoline F150 van. These older vehicles used simpler electronic control modules (ECMs) for various systems. These modules were essentially specialized computers that handled specific functions.
You'd find these ECMs in various locations within the van, often under the hood or tucked away in areas like under the dash. The specific location varied slightly depending on the options and configuration of the vehicle. A repair manual for your specific year and model would be the best resource to locate them.
