air pressure actuated brakes 36 air brake system 24 may be considered as including an air pressurization and storage subsystem including a compressor 16 storage tanks 18 and air lines 20 40 and 38 the details of air brake system 24 are otherwise conventional fig2 illustrates a conventional vehicle electrical control system 40 having a controller area network can bus 42 as its backbone can bus 42 conforms to the sae j1939 protocol and provides for data transmission between a plurality of controllers connected to the bus including an electrical system controller esc body computer 44 an engine control module 45 a stability and height controller 46 a transmission controller 48 a gauge controller 50 an auxiliary gauge controller 52 and an anti lock brake system abs controller 54 these controllers are generally attached to one or more devices the status of which may be transmitted over can bus 42 by its associated controller for the use of other controllers for example engine controller 45 is generally connected to a plurality of engine sensors 58 including among other sensors a crankshaft position sensor from which an engine tachometer indication may be developed transmission controller 48 controls a transmission 60 the output of which is measured by a drive shaft tachometer 62 this signal may be used to generate a measurement of vehicle speed a stability and height controller 46 controls the inflation of a plurality of air springs forming part of the vehicle suspension and represents an exogenous user of compressed air which complicates measurements of the performance of an air pressurization system gauge controller 50 and auxiliary gauge controllers 52 are often used to collect and format telemetry from vehicle sensors here various pressure sensors 70 including an air brake system pressure sensor are shown as.