Automobile sounds contain information on the technical state of the car; these sounds can be used to monitor the car while driving, and, in case of a flaw, to diagnose its source. For German car mechanics, listening to car sounds was, since the institutionalization of the trade in the 1930s, a legitimate entrance to diagnostic knowledge. The introduction of new diagnostic equipment in the 1950s contested the epistemic status of diagnostic listening. Manufacturers and trade authors claimed that these new testing instruments alone gave objective measurements, whereas old-fashioned bodily practices like diagnostic listening were too subjective and thus insufficient for automobile diagnostics. However, contesting the status of sensory diagnosis implicated the contestation of the car mechanics’ socio- technical position. This is why German mechanics did not embrace diagnostic technology until the 1980s and continued to deploy their sensory skills when diagnosing malfunctions.