If you’ve been diving into the world of diesel performance upgrades, you’ve probably come across terms like Powerstroke tuner harness plug and tuning modules more times than you can count. What Is a Tuner Harness Plug? A tuner harness plug is the physical adapter that connects your vehicle’s Engine Control Unit (ECU) to any external tuning device or performance module you plan to install. Understanding the Wiring ProcessSetting up your tuner harness plug for a Powerstroke engine doesn’t have to be overwhelming. The Role of Performance Parts in the Bigger PictureA tuner harness plug is just one piece of the puzzle.