Ignition switch (ST) and range switch (TR) in vehicles with automatic transmission
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When the ignition key is turned to the START position, battery voltage is applied to the range switch (TR) and from it to the engine control unit.
If the selector lever is not in position P or N, battery voltage will not be supplied to the control unit. Based on this signal, the control unit determines the operating mode of the automatic transmission and maintains the engine speed at the optimum level.