Where is the electronic spark control module on a 94 full size blazer 5.7?

The Electronic Spark Control (ESC) module on a 1994 Chevrolet Blazer 5.7L (likely a TBI system) isn't a standalone, easily identifiable module like some later systems. The spark control functions are integrated into the Throttle Body Injection (TBI) system's control module. This module is often called the Powertrain Control Module (PCM) or sometimes just the computer.

You won't find a separate "ESC module." Instead, look for the PCM. It's usually a fairly large, rectangular electronic control unit, often located under the hood, somewhere near the firewall, but its exact location can vary slightly depending on options and trim level. It might be bolted to the inner fender well, or secured to a bracket nearby.

Check your owner's manual (if you have it) for the precise location of the PCM or consult a repair manual specific to your 1994 Chevrolet Blazer 5.7L. A diagram in a repair manual will be invaluable.