A 1990 Chevy Truck 1500 5.7L doesn't have a single, easily identifiable "computer chip" like a modern car might. Instead, the engine control unit (ECU), often called the PCM (Powertrain Control Module) in GM vehicles, contains several integrated circuits (chips). This ECU is usually located somewhere within the engine compartment, often under the hood, but its exact location can vary depending on the specific model and trim level.
To find it, you'll need to consult a repair manual specific to your 1990 Chevy 1500 5.7L. The manual will have diagrams showing the location of the PCM. It's frequently a relatively large, rectangular black box, possibly with connectors and wiring harnesses attached. It might be mounted to the firewall, the inner fender, or even under the dash.
Without the specific repair manual, giving a precise location is impossible.
