Anelectronic control unit (ECU), also known as anelectronic control module (ECM), is anembedded system inautomotive electronics that controls one or more of theelectrical systems or subsystems in a car or othermotor vehicle.
Modern vehicles have many ECUs, and these can include some or all of the following:engine control module (ECM),powertrain control module (PCM), transmission control module (TCM), brake control module (BCM or EBCM), central control module (CCM), central timing module (CTM), general electronic module (GEM),body control module (BCM), and suspension control module (SCM). These ECUs together are sometimes referred to collectively asthe car's computer though technically they are all separate computers, not a single one. Sometimes an assembly incorporates several individual control modules (a PCM often controls both the engine and the transmission).[1]
Some modern motor vehicles have up to 150 ECUs.[2]Embedded software in ECUs continues to increase in line count, complexity, and sophistication.[3] Managing the increasing complexity and number of ECUs in a vehicle has become a key challenge fororiginal equipment manufacturers (OEMs).
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The development of an ECU involves both hardware and software required to perform the functions expected from that particular module. Automotive ECU's are being developed following the V-model.[1] Recently the trend is to dedicate a significant amount of time and effort to develop safe modules by following standards likeISO 26262.[5] It is rare that a module is developed fully from scratch. The design is generally iterative and improvements are made to both the hardware and software. The development of most ECUs is carried out by Tier 1 suppliers based on specifications provided by the OEM[citation needed].
As part of the development cycle, manufacturers perform detailedFMEAs and other failure analyses to catch failure modes that can lead to unsafe conditions or driver annoyance. Extensive testing and validation activities are carried out as part of theProduction part approval process to gain the confidence of the hardware and software.On-board diagnostics or OBD help provide specific data related to which system or component failed or caused a failure during run time and help perform repairs.
Some people may wish to modify their ECU so as to be able to add or change functionality. However modern ECUs come equipped with protection locks to prevent users from modifying the circuit or exchange chips. The protection locks are a form ofdigital rights management (DRM), the circumventing of which is illegal in certain jurisdictions. In theUnited States for example, theDMCA criminalizes circumvention of DRM,[6] though an exemption does apply that allows the owner of a motorized land vehicle circumvention if it is required to allow diagnosis, repair or lawful modification (ie. that does not violate applicable law such as emissions regulations).[7]
