In this paper I apply the mechanistic account of explanation to engineering science. I discuss two ways in which this extension offers further development of the mechanistic view. First, functional individuation of mechanisms in engineering science proceeds by means of two distinct sub types of role function, behavior function and effect function, rather than role function simpliciter. Second, it offers refined assessment of the explanatory power of mechanistic explanations. It is argued that in the context of malfunction explanations of technical systems, two key desiderata for mechanistic explanations, 'completeness and specificity' and 'abstraction', pull in opposite directions. I elaborate a novel explanatory desideratum to accommodate ...