SAE J1939 is an emerging communications protocol for on-board electronics in agricultural and construction equipment as well as for heavy duty on-highway equipment. The standard supports ECUs with both statically and dynamically configured addresses. This paper examines the dynamic addressing process, the process for ECUs that select addresses during initial power-up. A state diagram is proposed to implement the process described in the standard. Simulation results of systems with up to 100 dynamically configured ECUs are presented. Use of a pseudo-random delay after a power-ON self test was successful in minimizing bus-off collisions and allowed initialization times of under 1 second for 30 ECU systems. Minimum bus-off states during initialization of 30 ECU networks occurred with pseudo-random delays having a range of 0 to 15 ms.