A 1991 Pontiac Bonneville doesn't have a single, easily identifiable "computer" in the way modern cars do with a central ECU (Engine Control Unit). Instead, it uses several Electronic Control Modules (ECMs) or similar devices distributed throughout the vehicle to manage different systems. These would be more accurately described as "computers" than a single centralized unit. You won't find a box labeled "computer."
To find the main ECM related to the engine, you'll likely need to consult a repair manual specific to a 1991 Pontiac Bonneville. The location will vary depending on the engine and options. It's usually somewhere under the hood, but often tucked away and difficult to see without some disassembly. There may also be smaller control modules for other systems, like the automatic transmission, located elsewhere.
