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Back-Up Lamp

Fig 1: Identifying Brake Light
GLL161311Courtesy of VOLVO CARS CORPORATION

There are two reversing lights located in the tail lights. The reversing lights come on when reverse gear is selected. The reversing lights are connected to the central electronic module (CEM) via a directly connected relay. The lamps are powered via the relay.

Cars with manual transmissions 

Cars with manual transmissions have a back-up (reverse) switch on the transmission. The switch closes and transmits a directly connected signal to the central electronic module (CEM) when back-up (reverse) gear is selected.

Cars with automatic transmissions 

In cars with automatic transmissions, a signal is transmitted from the transmission control module (TCM) on the controller area network (CAN) to the central electronic module (CEM) indicating that back-up (reverse) gear is selected.

To detect faults in the reversing lights, the central electronic module (CEM) reads power consumption in the 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 (DIM).