Where is the Qaud Driver module located on a 1991 Buick Century Custom?

There isn't a "Quad Driver module" in the traditional sense in a 1991 Buick Century Custom. That terminology isn't standard automotive parlance. A 1991 Buick Century likely uses a more conventional system for controlling things like the ignition and fuel injection. The specific components would depend on the engine (3.3L V6 or 3.8L V6 were common).

To find the components that might be analogous to what you're looking for (perhaps you're thinking of a specific problem or part), you'd need to be more specific. Are you experiencing a particular problem? What are you trying to locate or repair?

For example, you might be looking for:

* The ignition control module (ICM): This controls the ignition system. Its location varies depending on the engine. Consult a repair manual for your specific engine.

* The Powertrain Control Module (PCM) or Engine Control Module (ECM): This is the computer that controls the engine and transmission. It's usually located under the dash or in the engine compartment, often protected by a cover. Again, a repair manual will pinpoint its location.

* A specific relay: If you're dealing with a particular electrical issue, there might be a relay involved. Relays are often found in fuse boxes under the hood or inside the car.

To get a precise answer, please describe the issue you're trying to address or the component you believe is failing. A 1991 Buick Century repair manual (available online or at auto parts stores) is your best resource for locating specific parts.