Turn Signals: Description and Operation

GF82.10-P-3008GM 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 flashing functions is the rear SAM control unit (N10/8).

The rear SAM control unit prioritizes all flashing functions and places a flasher frequency with the time period of the bright phase on the interior CAN (CAN B).

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

Additional function requirements, turn signaling
^ C. 15R On

The status of circuit 15 is placed on the interior CAN by the EIS [EZS] control unit (N73).

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 switch position of the combination switch (S4) is read in by the steering column tube module (N80) and made available on the engine compartment CAN (CAN C). The central gateway control unit (N93) forwards this via the interior CAN to the rear SAM control unit.

The rear SAM control unit passes on the request for output of the left turn signaling function as a flasher frequency to the corresponding control units on the interior CAN and actuates the following components:
- Left turn signal light (E3e1)
(without code (849) Spare tire holder/spare tire)
- Left turn signal light (E3/5e1)
(model 164 with code (849) Spare tire holder/spare tire)
- Left turn signal light on trailer via the trailer hitch socket, 13-pin (X58) (with code (550) Trailer hitch and without code (460) Canada version and without code (494) USA version) or the trailer hitch socket, 7-pin (X58/11) (with code (550) Trailer hitch and code (460) Canada version or code (494) USA version)

The front SAM control unit (N10) receives the flasher frequency and actuates the following components:
- Left turn signal light (E1e5) in left front lamp unit (E1)
- Left side marker lamp (E1e6) (model 164) in left front lamp unit

The left front door control unit (N69/1) receives the flasher frequency and actuates the left outside mirror turn signal light (E6/5) an.

Function sequence, right turn signal indicator
The switch position of the combination switch is read in by the steering column tube module and made available on the engine compartment CAN. The central gateway control unit forwards this via the interior CAN to the rear SAM control unit.
The rear SAM control unit passes on the request for output of the right turn signaling function as a flasher frequency to the corresponding control units on the interior CAN and actuates the following components:
- Right turn signal lights (E4e1)
(without code (849) Spare tire holder/spare tire)
- Right turn signal light (E4/5e1)
(model 164 with code (849) Spare tire holder/spare tire)
- Left turn signal light on the trailer via the trailer hitch socket, 13-pin or the trailer hitch socket, 7-pin

The front SAM control unit receives the flasher frequency and actuates the following components:
- Right turn signal light (E2e5) in right front lamp unit (E2)
- Right side marker lamp (E2e6) (model 164) in right front lamp unit

The right front door control unit (N69/2) receives the flasher frequency and actuates the right outside mirror turn signal light (E6/6).

In vehicles without code (460) Canada version and without code (494) USA version, the side marker lamps are usually actuated as well. In vehicles with code (460) Canada version or code (494) USA version, they are switched off after the first dark phase and then actuated in accordance with the flasher frequency.

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 turn signal light switch must only be operated briefly (t < 500 ms) in the desired turn signal direction.
Three flashing cycles are then output by the rear SAM control unit.

The one-touch turn signaling function is interrupted through actuation of the hazard warning flasher function or by operating the combination switch in the opposite direction.

Each active function is displayed to the driver through actuation of the left turn signal indicator lamp (A1e1) or right turn signal indicator lamp (A1e2) and the audible turn signal indicator (A1h2) in the instrument cluster (A1). The rear SAM control unit transmits the flasher frequency to the instrument cluster via the interior CAN for this purpose.

In the event of a turn signal light or turn signal lamp failure, the frequencies of the relevant indicator lamp, turn signal and audible turn signal indicator are acoustically doubled in the instrument cluster.
The flashing frequency of the turn signal lights and turn signal lamps is retained.

Function sequence, hazard warning flashing
The hazard warning flashing function is comprised of the following subfunctions:
^ Function sequence, hazard warning flashing, manual
^ Function sequence, hazard warning flashing for airbag deployment
^ Function sequence, hazard warning flashing for emergency braking
^ Function sequence, feedback of locking/unlocking of central locking system (CL) (without code (494) USA 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 flashing function is requested by activating the hazard warning system switch (N72/1s5). The status of the hazard warning system switch is read in directly by the upper control panel control unit (N72/1) and made available on the interior CAN. The function sequence of the hazard warning flasher system function - relative to the signal flow - corresponds to that of turn signaling. However, all turn signal lights and turn signal lamps on the vehicle and in vehicles with code (550) Trailer hitch are actuated synchronously on the trailer. The rear SAM control unit also sends the "hazard warning flashing active" status via the interior CAN to the upper control panel control unit, which then actuates the indicator lamp in the hazard warning system switch.

Depending on the position of the transmitter key (A8/1) in the EIS [EZS] control unit, the rear SAM control unit issues two duty cycles:
- With circuit 15R On: bright 58 %, dark 42 %
- With circuit 15R OFF: bright 35 %, dark 65 %

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

Function sequence, hazard warning flashing for airbag deployment
In the event of airbag deployment, the restraint systems control unit (N2/7) sends a corresponding signal to the engine compartment CAN.
The central gateway control unit routes this signal over the interior CAN to the rear SAM control unit.
The rear SAM control unit then initiates the hazard warning flashing system function by sending the flasher frequency to the interior CAN. Following this, all turn signal lights and turn signal lights on the vehicle are actuated synchronously.

This function is deactivated by operating the hazard warning system switch.

Additional function requirements, hazard warning flashing for emergency braking
^ Circuit 15 On
^ Emergency braking detected
(Brake Assist System active or vehicle deceleration at > 7.5 m/s 2)

Function sequence, hazard warning flashing for emergency braking
In the event of emergency braking the ESP control unit (N47-5) places a corresponding signal on the engine compartment CAN. The central gateway control unit routes this signal over the interior CAN to the rear SAM control unit.
The rear SAM control unit then initiates the hazard warning flashing system function by sending the flasher frequency to the interior CAN. All the turn signal lights and turn signal lamps on the vehicle are actuated synchronously for at least t = 1 s.

The hazard warning flasher for emergency braking is reset if one of the following conditions is met:
- Request of hazard warning flashing function by pressing the hazard warning system switch
- Brake released
- Vehicle speed v > 10 km/h

Function sequence, feedback from locking/unlocking of central locking (CL)
When the central locking system is locked/unlocked, the hazard warning flashing function is requested by the EIS [EZS] control unit via the interior CAN.
When the CL is unlocked the rear SAM control unit activates the hazard warning flashing function for one flasher cycle, when locking three flasher cycles are output.

Function sequence ATA flashing
If the antitheft alarm system is triggered, the rear SAM control unit initiates the hazard warning flashing system function by sending the flasher frequency to the interior CAN. Following this, all turn signal lights and turn signal lights on the vehicle are actuated synchronously.