This SAE Recommended Practice provides the framework to allow reprogramming software applications from all vehicle manufacturers the flexibility to work with multiple vehicle data link interface tools from multiple tool suppliers. This system enables each vehicle manufacturer to control the programming sequence for electronic control units (ECU’s) in their vehicles, but allows a single set of programming hardware and vehicle interface to be used to program modules for all vehicle manufacturers. This document does not limit the hardware possibilities for the connection between the PC used for the software application and the tool (e.g., RS-232, RS-485, USB, Ethernet…). Tool suppliers are free to choose the hardware interface appropriate for their tool. The goal of this document is to ensure that reprogramming software from any vehicle manufacturer is compatible with hardware supplied by any tool manufacturer. The U.S. Environmental Protection Agency (EPA) and the California Air Resources Board (ARB) have proposed requirements for reprogramming vehicles for all manufacturers by the aftermarket repair industry. This document is intended to meet those proposed requirements for 2004 model year vehicles. Additional requirements for the 2005 model year may require revision of this document, most notably the inclusion of SAE J1939 for some heavy-duty vehicles. This document will be reviewed for possible revision after those regulations are finalized and requirements are better understood. Possible revisions include SAE J1939 specific software and an alternate vehicle connector, but the basic hardware of an SAE J2534 interface device is expected to remain unchanged.