Digital signal processing (DSP) has been playing an increasingly important role in engine control and onboard diagnostics (OBD), a critical area of vehicle powertrain controls, to meet increasingly strict fuel efficiency requirements and emission regulations. This article gives an overview of DSP applications in this field from a practical perspective and identifies fruitful areas for DSP research and development in engine control and OBD. It also provides examples in the areas of engine misfire detection, individual cylinder fuel-air ratio imbalance detection, and engine knock detection.