The supply of power to most of the car's circuits is controlled by a specially designed element - the car's body control unit (VSM). The ignition switch is a low current switch with several discrete positions for a particular power mode. The power management unit also activates relays and other power distribution elements as needed. BCM determines the current power mode (off, on for accessories, fully on, starter engagement) and transmits this information to other power supplies via the data bus.
The table below shows the parameters of various power modes depending on the position of the ignition switch:
Ignition switch position | Diet | Ignition off / ignition on / starter on | Accessory Power/Engine Running | Engine running/ starter engaged |
Off (Off) Key removed | Bull. | Key removed / accessories | Not active | Not active |
Off (Off) Key inserted | Off | Key inserted/off | Not active | Not active |
Accessory (optional equipment) | Optional equipment | Key removed / accessories | Actively | Not active |
Run (engine running) | engine running | engine running | Actively | Actively |
Start (crankshaft rotation by starter) | crankshaft rotates | crankshaft rotates | Not active | Actively |
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