The ISX engine is equipped with an Electronic Diagnostic system. This is one of the most powerful pieces of the engine package. As the engine is operated, the diagnostic system receives critical information from electronic devices that are installed throughout the vehicle. It analyzes this information to identify engine failures and their causes.

When a failure occurs, the system alerts the operator through fault lamps or, if a RoadRelay is installed, using a visual display. In some severe cases, the engine will actually limit speed or power output to reduce the chance of progressive damage. The diagnostic system is also invaluable to the troubleshooting and repair process. The system logs a fault code and operating information at each failure event. These codes and supporting information can lead the service technician to the problem within seconds. Repairs are completed faster and more accurately, which means lower down time.

Should the vehicle be equipped with a Cummins RoadRelay 4 the operator will be alerted to a system fault through an audible alarm. In addition, RoadRelay will also provide important details concerning the fault including: the fault code, a short description of the fault, current status (Active or Inactive), recommended driver response and the number of times the fault has been experienced.