Model-Based Testing (MBT) uses a model of the System Under Test as reference to automatically derive test cases. Since it is often not reasonable to cover all the behaviours formalized in the model, coverage criteria are applied to select a relevant subset of model behaviours. In this paper, we propose a dedicated test coverage criterion, based on Def-Use criteria on signal exchange, to implement MBT approach from Systems Modeling Language (SysML) test models to validate mechatronic systems. This novel criterion is introduced and the relevance of the approach from SysML models is discussed regarding results obtained with a dedicated MBT toolchain implementing this criterion.