Turn Signals: Description and Operation

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

Turn signal light actuation function requirements, general
^ No overvoltage or undervoltage
(operating voltage range U ≥7 ≤17.5 V)

Turn signal actuation in general
The turn signal light actuation consists of all functions for output of the turn signal, various warnings and feedback. The master control unit for all turn signal functions is the front SAM control unit with fuse and relay module (N10/1).
The front SAM control unit prioritizes all flashing requests and transmits a flasher frequency with a time period of the bright phase of the turn signal lamps over the interior CAN (CAN B) to the corresponding control units.

Turn signal light actuation is comprised of the following subfunctions: ^ Operational sequence turn indicators
^ Function sequence, hazard warning flashing

Additional function requirements, turn signaling
^ Circuit 15R ON

The electronic ignition lock control unit (N73) sends the status of circuit 15 to the front SAM control unit via interior CAN.

Operational sequence turn indicators
The turn signaling function is comprised of the following subfunctions:
^ Function sequence, left turn signal indicator
^ Function sequence, right turn signal indicator
^ Function sequence, touch turn signal indicator

Function sequence, left turn signal indicator
The left turn signal function is requested by pushing the combination switch (S4) downward.
The steering column tube module control unit (N80) directly reads in the position of the combination switch and transmits it to the front SAM control unit via the chassis CAN (CAN E).

The front SAM control unit receives this, outputs the request for issuing the left turn signal function as a flasher frequency to the corresponding control units on interior CAN and actuates the left front turn signal light (E1e5).

The left front door control unit (N69/1) receives the flasher frequency and actuates the left outside mirror turn signal lamp (E6/5).
The rear SAM control unit with fuse and relay module (N10/2) receives the flasher frequency and actuates the left rear turn signal light (E3e1).
In vehicles with code (550) Trailer hitch, the trailer recognition control unit (N28/1) receives the flasher frequency and actuates the left turn signal light on the trailer via the trailer socket (X58).

Function sequence, right turn signal indicator
The right turn signal function is requested by pushing the combination switch upward.
The steering column tube module control unit reads in the position of the combination switch directly and transmits it to the front SAM control unit via the chassis CAN.

The front SAM control unit receives this, outputs the request for issuing the right turn signal function as a flasher frequency to the corresponding control units via interior CAN and actuates the right front turn signal light (E2e5).
The right front door control unit (N69/2) receives the flasher frequency and actuates the right outside mirror turn signal lamp (E6/6).
The rear SAM control unit receives the flasher frequency and actuates the right rear turn signal light (E4e1).
The trailer recognition control unit receives the flasher frequency and actuates the relevant turn signal light on the trailer via the trailer socket.

Function sequence, touch turn signaling
With regard to signal flow, the function sequence of the touch turn signal function corresponds to that of the left turn signal and right turn signal functions. The difference lies in the actuation and termination of the turn signal procedure. The combination switch must only be operated briefly (t < 440 ms) in the desired turn signal direction.

Three flashing cycles are output by the front SAM control unit. The one-touch turn signaling function is interrupted through actuation of the hazard warning flashing function or through actuation of the combination switch in the opposite direction.

The respective active function is displayed for the driver by means of actuation of the left turn signal light indicator lamp (A1e1) or right turn signal light indicator lamp (A1e2) and the audible turn signal light function check (A1h2). For this purpose, the instrument cluster (A1) receives the flasher frequency transmitted by the front SAM control unit via interior CAN. If a turn signal light or turn signal lamp fails, the frequencies of the turn signal indicator lamps and the turn signal light function check in the instrument cluster double to f = 3 Hz The flashing frequencies of the turn signal lights and the turn signal lamps f = 1.5 Hz remain the same.

Function sequence, hazard warning flashing
The function sequence for the manual hazard warning flasher is identical to that for turn signaling in terms of signal flow. However, all the turn signal lights and turn signal lights on the vehicle are actuated synchronously. In addition to the displays in the instrument cluster, the indicator lamp in the hazard warning flasher switch is actuated by the front SAM control unit via the instrument panel LIN (LIN 1).

Depending on the status of circuit 15, two duty cycles are output by the front SAM control unit:
^ With circuit 15R On: light 58 %, dark 42 %
^ With circuit 15R Off: light 35 %, dark 65 %

The active hazard warning flasher function is indicated by the turn signal light indicator lamps in the instrument cluster and the indicator lamp in the hazard warning flasher switch (S6/1s1). The front SAM control unit actuates the indicator lamp in the hazard warning flasher switch via the instrument panel LIN

The hazard warning flashing function is comprised of the following subfunctions:
^ Function sequence, hazard warning flashing, manual
^ Function sequence, hazard warning flashing for emergency braking
^ Function sequence, hazard warning flashing for airbag deployment
^ Function sequence, hazard warning flashing in the event of crash detection
^ Function sequence, feedback from locking/unlocking the central locking (CL) (without code (494) USA version and without code (460) Canada version)
^ Function sequence, anti-theft alarm system (ATA) flashing (with code (551) Antitheft alarm system (ATA))

Function sequence, hazard warning flashing, manual
The manual hazard warning flasher function is requested by pressing the hazard warning flasher switch.
The front SAM control unit reads in the status of the hazard warning flasher switch via instrument panel LIN.

Additional function requirements, hazard warning flashing for emergency braking
^ Circuit 15 On (transmitted by the electronic ignition lock control unit via the interior CAN)
^ Emergency braking within t = 500 ms recognized
(vehicle speed v > 70 km/h and Brake Assist System active or vehicle deceleration a > 7.5 m/s2 )

Function sequence, hazard warning flashing for emergency braking
In the event of emergency braking, the Electronic Stability Program control unit (N30/4) (without code (233) DISTRONIC PLUS) or the Electronic Stability Program Premium control unit (N30/7) (with code (233) DISTRONIC PLUS) sends a corresponding signal via chassis CAN to the front SAM control unit.

If, as a result of emergency braking, the vehicle was decelerated below the speed threshold of v > 3 km/h, the front SAM control unit activates the hazard warning flasher function during emergency braking by outputting the flasher frequency on the interior CAN.

All turn signal lights and the turn signal lamps on the vehicle are actuated synchronously.
The instrument cluster sends the vehicle speed to the front SAM control unit via interior CAN.
The hazard warning flashing function for emergency braking is reset if one of the following conditions is met:
- Request of the manual hazard warning flasher function
- Vehicle speed v > 10 km/h

Additional function requirements, hazard warning flashing for airbag deployment
^ Deceleration a > 4 g

Function sequence, hazard warning flashing for airbag deployment
If an airbag is deployed, the supplemental restraint system control unit (N2/10) transmits an appropriate signal to the front SAM control unit via the chassis CAN. The front SAM control unit initiates the hazard warning flashing function by outputting the flasher frequency on the interior CAN.

Afterwards all the turn signal lights and turn signal lamps on the vehicle are actuated synchronously.
This function is deactivated by operating the hazard warning flasher switch or by globally unlocking the central locking system.

Additional function requirements, hazard warning flashing for crash recognition
^ Vehicle deceleration a > 6 g

Function sequence, hazard warning flashing in the event of crash detection
A crash sensor is integrated in the front SAM control unit. If it recognizes an accident event during a timeout of the supplemental restraint system control unit, the front SAM control unit initiates the hazard warning flashing function by outputting the flasher frequency on the interior CAN. This prevents inadvertent activation of the local crash sensor.
All turn signal lights and the turn signal lamps on the vehicle are actuated synchronously.
This function is deactivated by operating the hazard warning flasher switch or by globally unlocking the central locking system.

Function sequence, feedback from locking/unlocking the CL (without code (494) USA version and without code (460) Canada version)
When the central locking system is locked/unlocked, the electronic ignition lock control unit requests the hazard warning flashing function via the interior CAN. The front SAM control unit activates the hazard warning flashing function for one flasher cycle when the central locking system is unlocked, and for three flasher cycles when the central locking system is locked.

Function sequence for ATA flashing
(with code (551) Anti-theft alarm system (ATA) [EDW])
When an ATA [EDW] alarm is triggered, the rear SAM control unit requests the hazard warning flashing function via interior CAN. The front SAM control unit generates an appropriate flasher frequency, which is output on the interior CAN. Afterwards all the turn signal lights and turn signal lamps on the vehicle are actuated synchronously.