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Home >> Volvo >> 2009 >> XC70 Base >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Electrical Modules And Components - Design And Function - 1 Of 5 >> Central Electronic Module (CEM) (2008-2012) >> Design >> Brake Light
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Brake Light

Fig 1: Identifying Brake Light
GLL161311Courtesy of VOLVO CARS CORPORATION

The stop lamps are in the tail lamps. The lamps light when the stop lamp switch on the brake pedal is closed. The stop lamp switch is connected to the central electronic module (CEM). The lamps are powered directly via an output on the central electronic module (CEM).

The stop lamps function even when the ignition is not on. When the ignition is not on, the central electronic module (CEM) is still powered. However the module is in a current saving mode. If the stop lamp switch is activated, the central electronic module (CEM) will also be activated and the stop lamps will come on.

To detect faults in the stop lamps, the central electronic module (CEM) reads the power consumption of the lamp circuit. If the power consumption falls below a certain limit, a fault is indicated and a text message is displayed in the driver information module.