Rear fog lamp

Fig 1: Identifying Rear Fog Lamp And Back-Up Lamp

Courtesy of VOLVO CARS OF NORTH AMERICA.

The rear fog lamp are in the tail lamps. The fog lamps are operated via a button in the light switch module (LSM). An LED in the button lights when the fog lamps are activated. The rear fog lamp can only be activated when low beam is on (market dependent). The light switch transmits information to the central electronic module (CEM) using serial communication when the button for the rear fog lamp is pressed. The central electronic module (CEM) transmits the data via the Controller area network (CAN) to the rear electronic module (REM). The power supply for the lamps is via a directly connected relay on the rear electronic module (REM).

When reactivating key position II, the function is set to non-activated mode.

In order to detect bulb faults for the rear fog lamp, the rear electronic module (REM) detects the power consumption in the circuit using a directly connected shunt. 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).

There are diagnostics for the rear fog lamp relay.