Immobilization, brief description
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Immobilization, brief description
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Ignition Switch Module, ISM (20)
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Control module, E39 ECM (590)
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Column Integration Module (CIM) (703)
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The column integration module (CIM) electronically checks that the key inserted in the ignition switch belongs to the car. A number of control modules in the car are included as part of the car's "immobilizer environment" and continuously transmit their ID numbers on the bus.
If the key is deemed OK and the control modules included in the immobilizer environment are transmitting the correct ID numbers, CIM will send the message "Immobilizer OFF" on the bus. This information is used by control module, E39, ECM, to cancel fuel shut-off, which is always activated before the engine is started.
