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Direction indicators, detailed description

Direction indicators, detailed description

The direction indicators are located in the headlamps, the front wings and the rear light clusters. Upon activation, CIM sends a message to the fuse boxes in the engine bay and luggage compartment, which control the direction indicators in the front and rear, respectively. Flash frequency is 90 flashes per minute. In the event of filament breakage, flash frequency is increased to 180 flashes per minute and a warning message is displayed in SID.


The car's direction indicators can be activated when the ignition switch is in the ON position. The direction indicator switch is fitted in the CIM (703). When the direction indicator stalk is moved up or down the CIM (703) sends the bus message "Direction indicator stalk active RIGHT" or "Direction indicator stalk active LEFT" respectively. The bus message is used by the BCM (707) which determines the rate of flashing. The BCM (707) sends bus messages (see Direction indicators and hazard warning lights, bus information ) which are used to control both the UEC (342) and the REC (701), but also for the light and acoustic indicator in the MIU (540).


Front direction indicators

The front direction indicators (27FL/FR) and side direction indicators (89LH/RH) are supplied power from UEC (342). The direction indicator function in UEC is controlled by bus messages from BCM. UEC activates the correct direction indicator output based on which bus messages are sent by BCM.

UEC supplies voltage to the front left direction indicator (27FL) from pin 3(F) and the side direction indicator (89LH) from output pin 4(F).

UEC supplies voltage to the front right direction indicator (27FR) from pin 2(F) and the side direction indicator (89RH) from output pin 9 (F).

Filament monitor

The UEC supplies current in each circuit. In the event of filament breakage in the front left direction indicator, for example, the UEC sends the bus message "Front left indicator not working" ON for pin 3(F). This bus message is used by the BCM (707) and the MIU (540). The BCM doubles flash frequency to 180 flashes per minute. A warning message is shown in the SID.


Rear direction indicators

Power is supplied to the rear direction indicators (27RL/RR) from REC (701). The direction indicator function in REC is governed by bus messages from BCM. REC activates the correct direction indicator function based on which bus messages BCM sends.

REC supplies power to the rear left direction indicator (27RL) from pin 8 (R-D) and to the rear right direction indicator (27RR) from pin 6 (R-D)

Filament monitor

The REC measures the current of the respective circuit. In the event of filament breakage or similar, the REC sends the bus message "Rear left indicator not working" ON for pin 8 (R-D) or "Rear right indicator not working" ON for pin 6 (R-D). This bus message is used by the BCM (707) and the MIU (540). The BCM doubles flash frequency to 180 flashes per minutes. A warning message is shown in the SID.

Indicator symbol in MIU

MIU uses the bus messages "Activate front left indicator ON" and "Activate front right indicator ON" to activate the indicator symbol for the left or right direction indicator.

Acoustic indicator

The MIU uses the bus messages "Activate front left direction indicator" ON and "Activate front right direction indicator" ON which activate the acoustic signal in the speakers in the MIU. The MIU handles the prioritising of all of the car's indicator and warning tone signals. If a warning message comes at the same time as the direction indicator is active then the direction indicator tone is discontinued for the time that the warning tone is active in the speakers. The warning tone has higher priority than the direction indicator tone.