Turn Signals: Description and Operation

GF82.10-P-3008RTE Turn Signal Indicator Actuation, Function

Component Identification:

General turn signal actuation function sequence
The turn signal actuation is comprised of several subfunctions.
These are:
^ Turn signals
^ One-touch turn signaling
^ Hazard warning flashing

Turn signal indicator flashing

Function requirements:
^ C. 15R On

Operational sequence turn indicators
The position of the combination switch is acquired by the steering column module, transmitted via CAN-C from the central gateway control unit to CAN-B and then relayed to the rear SAM control unit.

In its role as master control unit, the rear SAM control unit transmits each request for all the turn signal functions to CAN-B.

Left turn signal:
The front SAM control unit actuates the left turn signal light in the front left lamp unit (E1). The left front door control unit actuates the left outside mirror turn signal lamp.

The rear SAM control unit actuates the left turn signal light in the left taillamp (E3).

The rear SAM control unit also actuates (for code (550) Trailer hitch) the left turn signal lamps of the trailer via the trailer hitch socket.

Right turn signal:
The front SAM control unit actuates the right turn signal light in the front right lamp unit (E2). The right front door control unit actuates the right outside mirror turn signal lamp.

The rear SAM control unit actuates the right turn signal light in the right taillamp (E4).

The rear SAM control unit also actuates (for code (550) Trailer hitch) the left turn signal lamps of the trailer via the trailer hitch socket.

Feedback:
The instrument cluster receives the turn signal requests from the rear SAM control unit via CAN-B and actuates the left turn signal indicator lamp or the right turn signal indicator lamp and the audible turn signal indicator.
The flashing frequency is f = 1.5 Hz with a light/dark duty cycle of 52 % to 48 %.

If a faulty turn signal light or outside mirror turn signal lamp i detected, the frequencies of the turn signal indicator lamps and the audible turn signal indicator in the instrument cluster double. The frequency of the turn signal lights and outside mirror turn signal lamps remains at f = 1.5 Hz.

The turn signal procedure is ended following automatic reset when the vehicle is countersteered or through manual reset of the combination switch.

One-touch turn signaling

Function requirements:
^ C. 15R On

Turn signal lamp touch control, function sequence
The operational sequence for the turn signal lamp touch control is the same, in relation to the signal flow, as that for the turn signal indicator. The difference lies in the actuation and termination of the turn signal procedure.
For one-touch turn signaling, the combination switch may only be briefly (t < 500 ms) moved in the desired turn signaling direction. Provided the combination switch does not click into place, it triggers three turn signaling cycles.

One-touch turn signaling is ended by triggering the hazard warning flasher function or by operating the combination switch in the opposite direction.

Hazard warning flashers

The hazard warning flashers can be actuated as follows:
^ Manual activation
^ Automatic activation in event of airbag deployment
^ Requests from other systems

Manual activation

Function requirements:
^ C. 30 ON

Function sequence for activating manually
The hazard warning flasher is activated by pressing the hazard warning system switch. The hazard warning system switch is read in by the upper control panel control unit and forwarded to the rear SAM control unit via CAN-B. The function sequence for the hazard warning flasher is identical to that for turn signaling in terms of signal flow. However, the turn signal lights and outside mirror turn signal lamps on both sides of the vehicle are actuated.

The hazard warning flashing frequency is f = 1.5 Hz.
The duty cycle is dependent on the position of the transmitter key (A8/1) in the EIS [EZS] control unit (N73):
^ Circuit 15R ON: light 58 %, dark 42 %
^ Circuit 15R OFF: light 35 %, dark 65 %

Feedback:
In addition to the displays in the instrument cluster, the light emitting diode in the hazard warning flasher switch is actuated by the rear SAM control unit on CAN-B via the upper control panel control unit.

Automatic activation in event of airbag deployment

Function requirements:
^ Deceleration a > 4 g

Function sequence for automatic activation in event of airbag deployment
In the event of an airbag deployment, the restraint systems control unit transmits a signal via CAN-C to the central gateway control unit.
The central gateway control unit transmits this signal for actuating the corresponding turn signal lights and outside mirror turn signal lamps via CAN-B and then on to the rear SAM control unit. This function is deactivated by operating the hazard warning system switch or by globally unlocking the central locking.

Requests from other systems
When
^ locking/unlocking the vehicle using the central locking
^ upon triggering of the anti-theft alarm system (ATA [EDW]) (for code (551) Anti-theft alarm system (ATA {EDW]) and
^ following an emergency stop (reduction in speed from v ≥ 70 km/h to v = 0 km/h within a specific period of time) visual feedback is also given via the turn signal lights and the outside mirror turn signal lamps.