To manage the function of a vehicle's engine, transmission, and related subsystems, almost all modern vehicles make use of one or more electronic controllers running embedded software, henceforth referred to as a Powertrain Controller System or PCS. Fully validating this PCS is a necessary step of vehicle development, and the validation process requires extensive amounts of testing. Traditionally, this validation testing is done with open-loop signal generators, powertrain dynamometers, and real vehicles. Such testing methods either cannot simulate complex control system interactions, or are expensive and subject to variability. To address these concerns while decreasing development time and improving vehicle quality, Ford Motor Company is placing increasing focus on validating a PCS through simulation. One such testing method is a Hardware-in-the-Loop (HIL) simulation, which mates the physical elements of a PCS to a real-time computer simulation of a powertrain. A particular implementation of this testing method is Ford's VPACS (Virtual Powertrain and Control System) HIL system. VPACS-HIL provides a ‘Virtual Powertrain’ in the form of a proprietary closed-loop drivable powertrain model, running in real-time on a computer system that includes extensive signal input and output resources, with a proprietary electrical load system that automates electrical faulting.This paper will discuss the key attributes of the VPACS-HIL system, discuss the overall capabilities of Ford's VPACS-HIL lab, and review the primary applications of VPACS-HIL for PCS validation testing. This paper will also illustrate the benefits of VPACS-HIL through customer examples, including: increased rates of test completion, decreased cost per test, and more consistent test execution.