A universal power box for diagnosing, programming and powering an electronic control module includes at least one diesel engine control, a universal power box connector, and a diagnostic device connector. The power box connector is in circuit relationship to the diesel engine control and an electronic control module of a diesel engine. The diagnostic connector is in circuit relationship to the power box connector and a diagnostic device, which may be a third-party diagnostic device or a computer. A first wiring harness connects the power box connector to the vehicle side of the electronic control module. A second wiring harness connects the diagnostic device connector to the diagnostic device. A power source in circuit relationship to the power box connector provides power to the electronic control module when necessary.