Turn Signals: Description and Operation

GF82.10-P-3008LE 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 rear SAM control unit with fuse and relay module (N10/2) is the master control unit for all turn signal functions. 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). The flashing frequency is f = 1.5 Hz with a bright/dark duty cycle of 50 % to 50 %.

On model 221 as of 1.6.09 with code (615) Bi-xenon headlamp unit with integrated curve illumination or code (616) Bi-xenon headlamp unit with integrated asymmetric curve illumination or code (621) Intelligent Light System (left-hand traffic) or code (622) Intelligent Light System (right-hand traffic) light emitting diodes (LEDs) are used for output of the flashing functions instead of conventional incandescent bulbs. For this purpose, the left turn signal and cornering light voltage converter (E1n6) is located below the left front lamp unit (E1) and the right turn signal and cornering light voltage converter (E2n6) below the right front lamp unit (E2). These are supplied with power by the front SAM control unit with fuse and relay module (N10/1) and control the left turn signal light (E1e5) in the left front light unit and right turn signal light (E2e5) in the right front lamp unit.

LEDs are also used instead of conventional incandescent bulbs for output of the parking light and standing light functions. For this purpose, the left standing and parking light voltage converter (E1n5) and the right standing and parking light voltage converter (E2n5) are located below the front lamp units. These are supplied with power by the front SAM control unit and control the le standing and parking light (E1e3) in the left front light unit and right standing and parking light (E2e3) in the right front lamp unit. When the standing light control is active and the turn signal light actuation is requested, the front SAM control unit interrupts actuation of the LEDs located horizontally. The LEDs arranged vertically continue to be actuated.

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 EIS control unit (N73) sends the circuit status of circuit 15 to the rear SAM control unit via the 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 status of the left and right turn signal switch (S4s1) is read in directly by the steering column tube module (N80) placed on the chassis CAN (CAN E) and relayed to the rear SAM control unit via the interior CAN by the central gateway control unit (N93).

The rear SAM control unit receives the request to output the left turn signal function as a flasher frequency to the corresponding control units on the interior CAN and actuates the left turn signal light (E3e1) in the left taillamp (E3).
The front SAM control unit receives the flasher frequency and actuates the left turn signal light in the left front lamp unit. The left door control unit (N69/1) (model 216) or left front door control unit (N69/1) (model 221) receives the flasher frequency and actuates the left outside mirror turn signal lamp (E6/5).
The trailer recognition control unit (N28/1) (with code (550) Trailer hitch) receives the flasher frequency and actuates the corresponding turn signal lamp on the trailer by way of the trailer hitch socket, 13-pin (X58).

Function sequence, right turn signal indicator
The status of the turn signal switch is read in directly by the steering column tube module, sent to the chassis CAN and forwarded by the central gateway control unit via the interior CAN to the rear SAM control unit.
The rear SAM control unit sends the request to output the right turn signal function as a flasher frequency to the corresponding control units on the interior CAN and actuates the right turn signal light (E4e1) in the right taillamp (E4).
The front SAM control unit receives the flasher frequency and actuates the right turn signal light in the right front lamp unit. The right door control unit (N69/2) (model 216) or right front door control unit (N69/2) (model 221) receives the flasher frequency and actuates the right outside mirror turn signal lamp (E6/6).
The trailer recognition control unit receives the flasher frequency and actuates the corresponding turn signal lamp on the trailer via the trailer hitch 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 turn signal light switch must only be operated briefly (t < 500 ms) in the desired turn signal direction. Three flashing cycles are output by the rear SAM control unit. The touch turn signaling function is interrupted through actuation of the hazard warning flasher function or by pressing the turn signal 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). To do this, the central gateway control unit transmits the flasher frequency via the central CAN (CAN F) to the instrument cluster.

In the event of any failure in a turn signal light or turn signal lamp, the frequencies of the corresponding indicator lamp, turn signal and audible turn signal indicator are doubled-up in the instrument cluster.
The flashing frequency of the turn signal lights and turn signal lights of f = 1.5 Hz 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, feedback from locking/unlocking of central locking (CL)
^ Function sequence, anti-theft alarm system (ATA) flashing (with code (551) Antitheft alarm system (ATA))
^ Function sequence for hazard warning flasher during taxi alarm (model 221 with code (934) Taxi emergency alarm system)

Function sequence, hazard warning flashing, manual
The hazard warning flasher function is requested by pressing the hazard warning system button (A40/9s3).
The status of the hazard warning system button (N72/1) is read in by the upper control panel control unit and forwarded via the interior CAN to the rear SAM control unit. 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 trailer (with code (550) Trailer hitch) are actuated synchronously. The rear SAM control unit also sends the "hazard warning flasher active" status via the interior CAN to the upper control panel control unit, which then actuates the indicator lamp in the hazard warning system button.

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 50 %, dark 50 %
- 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 chassis 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.

When the hazard warning system button is pressed the hazard warning flasher function is deactivated during airbag deployment.

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 central locking system is unlocked, the rear SAM control unit activates the hazard warning flashing function for one flasher cycle, when locking three flasher cycles are issued.
The flashing frequency here is f = 1.5 Hz with a bright/dark duty cycle of 50 % to 50 %.

Function sequence for ATA flashing(with code (551) Anti-theft alarm system (ATA [EDW]))
If the antitheft alarm system is triggered, the rear SAM control unit initiates the hazard warning flasher system function by sending the flasher frequency to the interior CAN.

The type and duration of alarm has to be programmed using the diagnosis in the rear SAM control unit.

Function sequence for hazard warning flasher during taxi alarm (model 221 with code (934) Taxi emergency alarm system)
When a taxi alarms is triggered, the special vehicle multifunction control unit (MSS) (N26/9) sends a corresponding signal with the duration of the bright phase via the interior CAN to the rear SAM control unit.
The signal is sent in a cycle of t = 100 ms.
The rear SAM control unit then initiates the hazard warning flashing system function by sending the flasher frequency to the interior CAN.
In the instrument cluster and hazard warning flasher switch the corresponding indicator lamps are actuated.
This function is deactivated if the signal from the multifunction control unit does not appear for t > 1 s.