Exterior Lighting Systems Description and Operation
Exterior Lamps
The exterior lighting system consist of the following lamps:
| • |
Automatic Headlamp
Leveling |
| • |
Adaptive Forward
Lighting |
| • |
Daytime Running Lamps
(DRL) |
| • |
Park, Tail, License and Marker
Lamps |
Low Beam Headlamps (Standard) RPO T4A
The headlamps consist of 2 interchangeable single filament bulbs
or 2 high intensity discharge (HID) arc tubes and ballast on each
side of the vehicle which provide high and low beams. The lower
bulb in the headlamp is the high beam and the upper bulb is the low
beam.
The headlamps may be turned ON in 3 different ways:
| • |
When the headlamp switch is
placed in the ON position, for normal operation |
| • |
When the headlamp switch is
placed in the AUTOMATIC LIGHT position, for automatic lamp
control |
| • |
When the headlamp switch is
placed in the AUTOMATIC LIGHT position, with the windshield wipers
ON in daylight conditions, after a 6 s delay |
The body control module (BCM) controls the headlamps based on
the inputs explained above. When a low beam request is received,
the BCM supplies a B+ through the headlamp low beam relay for the
headlamps and through the daytime running lamp relay right for the
right headlamp. This then applies B+ to the low beam headlamps,
illuminating the low beam headlamps. When a high beam request is
received, the BCM grounds the headlamp high beam relay control
circuit. This energizes the coil in the headlamp high beam relay,
causing the relay switch to close. This then applies B+ to both
high beam headlamps through the left high beam and right high beam
fuses, illuminating the high beam headlamps.
High Intensity Discharge (HID) Low Beam Headlamps (Up Level)
RPO T4F/T95
The BCM controls the headlamps based on the inputs explained
above. When a low beam request is received, the BCM grounds the
headlamp low beam relay control circuit. This energizes the coil in
the headlamp low beam relay, causing the relay switch to close.
This then applies B+ to both low beam HID headlamps through the
left low beam and right low beam fuses, illuminating the low beam
headlamps. When a high beam request is received, the BCM grounds
the headlamp high beam relay control circuit. This energizes the
coil in the high beam relay, causing the relay switch to close.
This then applies B+ to both low beam HID headlamps through the
left high beam and right high beam fuses, illuminating the high
beam headlamps.
Run Up of the Lamp
Each ballast requires higher amperage in order to ensure normal
startup and run up of the lamp. Run up is the term used to describe
the extra power level given to the bulb. The input current during
the steady state operation is lower that the start up amperage.
After the lamp receives the strike from the starter and the arc is
established, the ballast uses its operating voltage in order to
provide the run up power needed in order to keep the lamp ON. The
lamp rapidly increases in intensity from a dim glow to a very
high-intensity, bright light called a steady state. Within a few
seconds of the arc being established in the bulb, the majority of
steady state is complete. 100 percent of the steady state is
completed shortly there after. A high watt power level is necessary
in order to bring the lamp to a steady state in such a short period
of time. The high watt power level allows the lamp to meet the SAE
light vs. time specification.
When to Change the HID Bulb
An inoperative bulb, end of life occurs when the bulb gets old and
becomes unstable. The bulb may begin shutting itself OFF
sporadically and unpredictably at first, perhaps only once during a
24 h period. When the bulb begins shutting itself off occasionally,
the ballast will automatically turn the bulb back ON again within
0.5 s. The ballast will restrike the bulb so quickly that the bulb
may not appear to have shut off. As the bulb ages, the bulb may
begin to shut off more frequently, eventually over 30 times per
minute. When the bulb begins to shut off more frequently, the
ballast receives an extreme amount of repetitive current input .
Repetitive and extreme amount restarts or restrikes, without time
for the ballast to cool down, will permanently damage the ballast.
As a safeguard, when repetitive restrikes are detected, the ballast
will not attempt to restrike the lamp. The ballast then shuts down
and the bulb goes out.
The following symptoms are noticeable signs of an inoperative
bulb:
| • |
Flickering light, caused in
the early stages of an inoperative bulb |
| • |
Lights go out, caused when the
ballast detects, repetitive bulb restrike |
| • |
Color change - The lamp may
change to a dim pink glow. |
Input power to the ballast must be terminated in order to reset
the ballasts fault circuitry. In order to terminate the input power
to the ballast, turn the lights OFF and back ON again. Turning the
lights OFF and back ON again resets all of the fault circuitry
within the ballast until the next occurrence of an extreme amount
of repetitive bulb restrike. When an extreme amount of repetitive
bulb restrikes occur, replace the starter/arc tube assembly. The
ballast will begin the start-up process when the starter/arc tube
assembly is replaced. Repeatedly resetting the input power can
overheat the internal components and cause permanent damage to the
ballast. Allow a few minutes of cool-down time in between reset
attempts.
Inoperative bulbs are often sporadic at first, and difficult to
repeat. Inoperative bulbs can be identified by observing if the
condition gets progressively worse over the next 100 h of
operation.
Light Color
White light has a different color rating than regular headlamps.
The range of white light that is acceptable is broad when compared
to halogens. Therefore, some variation in headlight coloring
between the right and left headlamp will be normal. One HID at the
end of the normal range may appear considerably different in color
from one at the other end of the range. Difference in color is
normal. Replace the arc tube only if the arc tube is determined to
be at the bulb inoperative stage.
Adaptive Forward Lighting
The adaptive forward lighting consist of the following
components:
| • |
Headlamp control module
|
| • |
Headlamp actuator -
left |
| • |
Headlamp actuator -
right |
Dynamic Curve Light
Bend lighting is a function depending on the following signal input
values:
The appropriate swivel angle is calculated based on vehicle
speed and the steering angle value.
Cornering Light
The cornering lamp is activated automatically at vehicle speeds
below 40 km/h (25 MPH) when the direction indicator is switched ON
and/or when the steering angle is changed from the straight-ahead
position towards the side the vehicle is going to turn and passes a
programmable angle threshold. The cornering lamp is deactivated
automatically when the direction indicator is switched OFF and/or
the steering angle has returned in the straight-ahead position. The
cornering lamps are deactivated at vehicle speeds above 40 km/h (25
MPH). If reverse gear is active, the cornering lamps go into park
function. Both lamps will be switched on. They will switch off 20 s
after leaving reverse gear or if the vehicle speed exceeds 7 km/h
(4 MPH). The cornering lamps also provide a protection against
overheating. When having been continuously switched on for 2 min,
adaptive forward lighting will deactivate the lamps for 2 min to
enable cooling down.
Town Light
Town Light is activated while the vehicle speed is below 55 km/h
(34 MPH) as well as the light sensor detects street lights and the
town road category is detected. The light distribution is reduced
to an area near the car due to low speeds.
Motorway Light
If vehicle speed is above 100 km/h (62 MPH) for at least 20 s (or
once above 126 km/h (78 MPH) and the corresponding road category is
identified, the headlamps will be switched to a motorway light
distribution. During motorway light the light output of the HID
bulb is increased to 38 W by electrical power management. This
improves the visibility range at the far end of the road.
Country Light
Country light replaces the current low beam and will be controlled
based on programmable vehicle thresholds as well as corresponding
road detection. The vehicle speed has to be between 55 km/h (34
MPH) and 100 km/h (62 MPH). Country light is the default light
distribution at 35 W. Light distribution is reduced on the left
side to prevent oncoming traffic from being dazzled.
Tourist Mode
The tourist mode functionality switches the adaptive forward
lighting headlamps into a non dazzling mode, if the traffic
regulation moves from left hand traffic to right hand traffic and
vice versa. The functionality is switched on/off with the same
stalk/switch combination. The "flash to pass" stalk needs to be
activated while ignition is switched on (System Power Mode = RUN).
The "flash to pass" stalk remains activated until the warning
indicator within the instrument panel cluster starts flashing (4 s)
and an acoustic indication is sent. The activation period takes
about 3 s. An activation flag must be set within the adaptive
forward lighting ECM and stored in non-volatile memory. Each time
the ignition is switched on and the tourist mode is active, the
warning indicator is flashing about 4 s. The tourist mode is
deactivated with the same procedure described above. The function
is switched OFF, if an acoustic signal is sent (Warning indicator
remains inactive).
Adverse Weather Light
Adverse weather light will be switched on while the vehicle speed
is below 100 km/h (62 MPH) and the windscreen wipers are activated.
The HID bulbs will be powered with different values:
The main advantage is that reflections on the wet floor are
reduced to a minimum. This is noticeable as well for oncoming
traffic as for the driver. In front of the car a less illuminated
area is realized.
Automatic Lamp Control
Automatic Light is switched ON as default. It can be switched
OFF by turning the light switch to OFF position. It will be
switched ON again by doing so again. Automatic Light is only
available if a rain sensor or rain/light sensor module in installed
in the car. The rain/light sensor module will send the actual
ambient light state (day/night) to the BCM. If Automatic Light is
enabled, BCM will react on the message received from the rain/light
sensor module by switching ON/OFF low beams.
Flash to Pass (Standard) RPO T4A
When the low beam headlamps are on and the turn
signal/multifunction switch is momentarily placed in the flash to
pass position, ground is applied to the turn signal/multifunction
switch. The turn signal/multifunction switch applies ground to the
BCM through the flash to pass switch signal circuit. The BCM then
applies ground to the high beam relay control circuit. This
energizes the high beam relay, closing the switch side contacts of
the high beam relay, applying battery voltage to the left and right
high beam fuses. Battery voltage is applied from the high beam
fuses through the high beam voltage supply circuit to the high beam
headlamp assemblies. This causes the high beam headlamps to
illuminate at full brightness momentarily or until the flash to
pass switch is released.
Flash to Pass (Up Level) RPO T95
When the low beam headlamps are ON and the turn
signal/multifunction switch is momentarily placed in the flash to
pass position, ground is applied to the turn signal/multifunction
switch. The turn signal/multifunction switch applies ground to the
BCM through the flash to pass switch signal circuit. The BCM sends
a message to the headlamp control module to lift the shutter from
the Xenon lamp. This causes the Xenon lamp to illuminate the
headlamp at full brightness momentarily or until the flash to pass
switch is released.
High Beam Select Module
The high beam system is a convenience feature that may have
safety benefits. The system should support the driver in the use of
the high beams. So the high beams should be switched on as often as
possible. The high beam select module system automates the task of
switching between high and low beam headlamp functions in response
of detect lighting of the presence or absence of oncoming and
preceding vehicles. The system only operates in night ambient light
conditions and is functional, when the main lighting switch is
determined to be in AUTO. For systems that have a xenon headlamp,
the BCM will control the activation/deactivation of the high beams
based on requests from the high beam select module.
The following reasons cause a switch-off of the high beams:
| • |
Ambient light level too high
in due to towns or twilight situations |
| • |
Vehicle speed greater than 40
km/h (25 MPH) |
| • |
Fog or snow, the high beam
select module is deactivated for 2 min, thereafter it is checked
again |
Activation/Deactivation of Smart Beam Function
Smart beam will be active when power mode becomes RUN. The main
lighting switch has to be determined as AUTO and the ambient light
must be night. The driver can deactivate the system by manually
deactivating or activating the high beam via high beam switch.
Smart beam will then be turned off. It can be reactivated by
pushing the high beam switch twice within two seconds.
High Beam Select Module Indicator
The status of high beam select module is shown by a green indicator
in the instrument panel cluster. If smart beam is active, the
indicator will be switched on continuously. If the driver
deactivates the system, the indicator will switch-off.
Identification of Approaching/Preceding Vehicles
The high beam select module is equipped with a camera module.
Thereby it is able to identify approaching vehicles as soon as
possible. On an even, straight road vehicles can be identified at a
distance of greater than 0.4 km (0.25 mi).
Tourist Mode
The tourist mode functionality switches the high beam select module
headlamps into a non dazzling mode, if the traffic regulation moves
from left hand traffic to right hand traffic and vice versa.
Village Detection
The high beam select module performs an internal village detection.
If the high beam select module detects a village, it stops
controlling/requesting high beam activation and turns off the high
beam lights. Nevertheless, the high beam select module and the
indicator will still be active.
Fog Lamps
The high beam select module is enabled automatically when the front
or rear fog lamps are turn on.
Automatic Headlamp Leveling RPO TR7
The Automatic Headlamp Leveling Systems consist of the following
components:
| • |
Headlamp leveling actuator -
left |
| • |
Headlamp leveling actuator -
right |
| • |
Headlamp control module
|
| • |
Headlamp leveling sensor -
front |
| • |
Headlamp leveling sensor -
rear |
The automatic headlamp leveling system automatically maintains
the vertical alignment of the headlamps when the vehicle load and
driving conditions change. The headlamp control module receives
inputs from the front and rear headlamp leveling sensors to
determine vehicle pitch. The headlamp leveling sensors send an
output to the headlamp control module as the vehicle suspension
compresses and rebounds. The headlamp control module calculates the
difference in vehicle pitch and sends a command to the (HID)
ballast. The ballast then drive the headlamp leveling actuators to
the position commanded by the headlamp control module. The headlamp
leveling system also monitors the performance of the HID bulb and
ballast. When the headlamp switch is placed in the ON position the
headlamps will go down, and then back up to the center
position.
Daytime Running Lamps (DRL) without HID RPO T4F/T95
The DRL bulbs are combined with the park lamps. One filament is
for the DRL and one for the park lamps. The DRL will operate when
the following conditions are met:
| • |
Headlamp switch in AUTOMATIC
LIGHT position. |
| • |
The high and low beam
headlamps are OFF. |
By turning the headlamp switch in the OFF position the automatic
light function and the DRL will be deactivated.
The ambient light sensor is used to monitor outside lighting
conditions. The ambient light sensor provides a voltage signal that
will vary between 0.2-4.9 V depending on outside lighting
conditions. The HVAC control module provides a low reference ground
and 5 V reference signals to the ambient light sensor. The BCM
monitors the ambient light sensor signal circuit to determine if
outside lighting conditions are correct for either DRL or low beam
when the headlamp switch is in the AUTOMATIC LIGHT position. In
daylight conditions, the BCM will command the DRL ON by applying
ground to the left and right DRL relays via separate left and right
DRL relay control circuits. When the BCM applies ground to the
relay control circuits, the left and right DRL relay coils energize
causing both relay switch contacts to close. With the left and
right DRL relay switch contacts closed, battery voltage flows to
the left and right DRL lamps. Any function or condition that turns
on the headlamps will cancel DRL operation.
Daytime Running Lamps (DRL) with HID RPO T4F/T95
The DRL are LEDs which are continuously illuminated when:
| • |
Ignition is switched
ON. |
| • |
High and low beam headlamps
are ON or OFF. |
| • |
Headlamp switch is in PARKING
LIGHT, AUTOMATIC LIGHT or LOW BEAM position. |
By turning the headlamp switch in the OFF position the automatic
light function and the DRL will be deactivated.
The ambient light sensor is used to monitor outside lighting
conditions. The ambient light sensor provides a voltage signal that
will vary between 0.2-4.9 V depending on outside lighting
conditions. The HVAC control module provides a low reference ground
and 5 V reference to the ambient light sensor. The BCM monitors the
ambient light sensor signal circuit to determine if outside
lighting conditions are correct for only DRL or DRL and low beam
when the headlamp switch is in the AUTOMATIC LIGHT position. In
daylight conditions the BCM will command the DRL ON.
Front Fog Lamps
The front fog lamp relay is supplied with battery voltage at all
times. The front fog lamp switch signal circuit is grounded
momentarily by pressing the front fog lamp switch. The body control
module (BCM) energizes the front fog lamp relay by applying ground
to the front fog lamp relay control circuit. When the front fog
lamp relay is energized, the relay switch contacts close and
battery voltage is applied through the front fog lamp fuse to the
front fog lamp supply voltage circuit which illuminates the front
fog lamps.
Rear Fog Lamps
When the rear fog lamp switch is placed in the ON position,
battery voltage is applied from the BCM to the rear fog lamps.
Ground for the rear fog lamps is applied at all times.
The BCM will send a message via GMLAN serial data to the
instrument panel cluster to enable the rear fog lamp indicator.
Park, Tail, License and Marker Lamps
The park lamps, tail lamps/LEDs and number plate lights are
turned ON when the headlamp switch is placed in the Parking lights
or Low beam position or anytime the headlights are requested. When
the BCM receives a request from the headlamp switch to turn ON the
park lamps the BCM a sends out a PWM signal, which illuminates the
park lamps, tail lamps and number plate lights.
Turn Signal Lamps
Ground is applied at all times to the turn signal/multifunction
switch. The turn signal lamps may only be activated with the
ignition switch in the ON or START position. When the turn
signal/multifunction switch is placed in either the TURN RIGHT or
TURN LEFT position, ground is applied to the BCM through either the
right turn or left turn signal switch signal circuit. The BCM then
applies a pulsating voltage to the front and rear turn signal lamps
through there respective voltage supply circuits. When a turn
signal request is received by the BCM, a serial data message is
sent to the instrument cluster requesting the respective turn
signal indicator be pulsed ON and OFF.
Repeater Lamps
The repeater lamps are located in the front fender. The repeater
lamps are used as additional turn signal lamps, and operate as
described in the Turn Signal/Hazard Flasher Lamps description.
Hazard Flasher Lamps
The hazard flashers may be activated in any power mode. The
hazard switch is permanently grounded. When the hazard switch is
placed in the ON position, ground is applied through the hazard
switch signal circuit to the BCM. The BCM supplies battery voltage
to all turn signal lamps in an ON and OFF duty cycle. When the
hazard switch is activated, the BCM sends a serial data message to
the instrument cluster requesting both turn signal indicators to be
cycled ON and OFF.
Stop Lamps
The brake pedal position (BPP) sensor is used to sense the
action of the driver application of the brake pedal. The BPP sensor
provides an analog voltage signal that will increase as the brake
pedal is applied. The BCM provides a low reference signal and a 5 V
reference voltage to the BPP sensor. When the variable signal
reaches a voltage threshold indicating the brakes have been
applied, the BCM will apply battery voltage to the stop lamp
control circuit and center high mounted stop lamp control circuit.
When the control circuit is energized the stop lamps are
illuminated.
Backup Lamps
When the transmission is placed in the reverse position, the
engine control module (ECM) sends a serial data message to the BCM.
The message indicates that the gear selector is in the reverse
position. The BCM applies battery voltage to the backup lamps. The
backup lamps are permanently grounded. Once the driver moves the
gear selector out of the reverse position, a message is sent by the
ECM via serial data requesting the BCM to remove battery voltage
from the backup lamp control circuit.
Battery Run Down Protection/Inadvertent Power
To provide battery run down protection, the exterior lamps will
be deactivated automatically under certain conditions. The BCM
monitors the state of the headlamp switch. If the park or headlamp
switch is ON when the ignition switch is placed in either the CRANK
or RUN position and then placed in the OFF position, the BCM
initiates a 10 min timer. At the end of the 10 min, the BCM will
turn OFF the control power output to the park and headlamp relay
coils, deactivating the exterior lamps. This feature will be
cancelled if any power mode other than OFF becomes active. The BCM
will disable battery run down protection if any of the following
conditions exist. The park or headlamp switch is placed in the ON
to OFF position, and back to the ON position during battery run
down protection. The BCM determined that the park or headlamp
switch was not active when the ignition was turned OFF.
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