Fog/Driving Lamp: Description and Operation

GF82.10-P-3070GM Front Fog Light Actuation, Function

Function requirements, front fog light actuation, general
^ No overvoltage or undervoltage
(operating voltage range U ≥7 ≤17.5 V)
^ Standing lights on (rotary light switch (S1) in "Standing lights" or "Manual driving lights" position) in vehicles with code (460) Canada version or code (494) USA version only in "Manual driving lights" position
^ Circuit 15 on (if coded)

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

Front fog light actuation in general
Front fog light actuation provides better illumination of the road while driving as well as illuminating the rear of the vehicle under bad weather conditions.

During front fog light actuation standing/parking lights actuation is also active, which is described in a separate document.

The front fog light actuation is comprised of the following subfunctions:
^ Front fog lamp actuation function sequence
(Model 164.1, model 251.0/1, model 164.8 up to 30.6.09 and as of 1.7.09 with code (498) Japan version or without code (615) Bi-xenon headlamp unit with integral curve illumination and without code (616) Bi-xenon headlamp unit with integral asymmetrical curve illumination and without (621) Intelligent Light System (left-hand traffic) and without code (622) Intelligent Light System (right-hand traffic))
^ Rear fog light actuation function sequence

Front fog lamp actuation function sequence
Pulling out the rotary light switch up to the first notch requests actuation of the front fog lamps.
The status of the rotary light switch is read in by the upper control panel control unit (N72/1) via the instrument panel LIN (LIN 1) and made available on the interior CAN.

The front SAM control unit (N10) reads this in, actuates the left front fog lamp (E5/1) and the right front fog lamp (E5/2) and transmit "Front fog lamp actuation active" status via the interior CAN to the upper control panel control unit.
The upper control panel control unit then actuates the front fog lamp indicator lamp (S1e1) in the rotary light switch, therefore signaling that front fog lamp actuation is active.
When the automatic lamp substitution function is requested, the front fog lamps are actuated corresponding to the requested automatic lamp substitution function.

In vehicles with code (460) Canada version or code (494) USA version, the front fog lamps and the high beams function may not be actuated simultaneously.
The current incoming request has priority.

Rear fog light actuation function requirements
^ Rotary light switch set to manual driving lights

Rear fog light actuation function sequence
Rear fog light actuation is requested by pulling out the rotary light switch until the first detent (vehicles without front fog lamps) or the second detent (vehicles with front fog lamps).
The status of the rotary light switch is read in by the upper control panel control unit via the instrument panel LIN and made available on the interior CAN.
The front SAM control unit reads this in and transmits the "Switch on rear fog light" request via the interior CAN to the rear SAM control unit (N10/8).

The rear SAM control unit actuates the following components in accordance with the country coding:
- Model 164:
- Left taillight and rear fog light (E3e2) or
- Right taillight and rear fog light (E4e2)
- Left or right rear fog lamp on trailer (with code (550) Trailer hitch)

- Model 251:
- Left rear fog light (E3e5) or
- Right rear fog light (E4e5)
- Left or right rear fog lamp on trailer (with code (550) Trailer hitch)

In Economic Commission for Europe (ECE) vehicles the right taillight, side marker lamp and parking light (E3e8) or the right taillight, side marker lamp and parking light (E4e8) are actuated with output of P = 21 W and used as the rear fog light.

The rear fog light on the vehicle is not actuated during trailer operation.
In vehicles with code (460) Canada version or code (494) USA version, the trailer does not have a rear fog light.

The front SAM control unit transmits the "Rear fog light actuation active" status via the interior CAN to the upper control panel control unit, which then actuates the rear fog light indicator lamp (S1e2) in the rotary light switch via the instrument panel LIN. Active rear fog light actuation is signaled by illumination of the front fog lamp indicator lamp.

If the transmitter key (A8/1) is removed from the EIS [EZS] control unit when the rear fog light actuation is active, and then the driver door is opened, the instrument cluster (A1) actuates the warning buzzer (A1h1) and issues an appropriate message on the multifunction display (A1p13).
The request to deactivate rear fog light actuation via the rotary light switch prevents the rear fog light actuation from being activated automatically the next time the vehicle is driven with the low beams switched on.