Drl Circuit Description; (Chevrolet And Pontiac/Canadian); (Pontiac Domestic); Fog Lights Circuit Description - GMC Chevrolet Camaro 1998 Service Manual

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Body and Accessories
DRL Circuit Description
(Chevrolet and Pontiac/Canadian)
The Daytime Running Lamps (DRL) module is
designed to automatically operate the exterior lights
depending on the outside light conditions.
The DRL module operates in 2 modes:
• The day mode
In the day mode, the DRL module turns on the
low beam headlamps at a reduced intensity when
the DRL ambient light sensor detects daylight
under the following conditions:
- The ignition switch is in the RUN position.
- The headlamps are OFF.
- The park brake is OFF.
• The low light mode
In the low light mode, the DRL ambient light
sensor detects darkness, turning on the low beam
headlamps to full intensity through CKT 10.
Additionally, the DRL ambient light sensor turns
on the following lamps through CKT 9:
- The park lamps
- The tail/stop lamps
- The license lamps
- The tail lamps
- The park/turn lamps
- The tail/stop/turn lamps
If the engine stalls with the DRL module in the low
light mode, the DRL module turns off the headlamps
while the engine is being cranked. The DRL module
turns on the following lamps while the engine is
being cranked:
• The park/turn lamps
• The park lamps
• The license lamps
• The tail lamps
• The tail/stop lamps
• The tail/stop/turn lamps
The following lamps operate in the usual manner:
• The headlamp
• The instrument panel lamp dimmer switch
The DRL module receives voltage from the
following fuses:
• The TAIL LPS fuse through CKT 240
• The TURN B/U fuse through CKT 141
The following lamps may be operated manually at any
time by using the headlamp and the instrument
panel lamp dimmer switch:
• The park lamps
• The headlamps
The DRL module does not operate if the system
voltage is less than 9 volts or greater than 18 volts.
Lighting Systems 8-157
Daytime Running Lamps (DRL) Ambient
Light Sensor
The DRL ambient light sensor is a light sensitive
variable resistor. The DRL ambient light sensor's
resistance decreases as the outside light intensity
increases. The DRL module performs the following
functions:
• Measures the voltage drop across the DRL
ambient light sensor.
• Determines whether the DRL ambient light sensor
should operate in the day mode or the low
light mode.
Park Brake Input
The DRL module will not operate any headlamps or
exterior lamps if the park brake is applied before
the ignition switch is turned to the RUN position. This
allows the driver to start the vehicle and keep the
headlamps OFF, as long as the park brake is applied.
The DRL module activates the headlamps when
the park brake is released with the ignition switch in
the RUN position. This feature functions only when the
park brake is applied before the ignition switch is
turned to the RUN position. The headlamps will not
turn OFF, if the park brake is applied after the ignition
switch is turned to the RUN position.
DRL Circuit Description
(Pontiac Domestic)
Daytime Running Lamps (DRL)
The Daytime Running Lamps (DRL) module is
designed to automatically operate the exterior lights
depending on the outside light conditions. The ambient
light sensor is replaced by a jumper.
The DRL module operates when the following occurs:
• The ignition switch is in the RUN position.
• The headlamps are OFF.
• The park brake is OFF.
The DRL module applies voltage to the front turn
signal bulbs. Whenever the left or the right turn input
is received at the DRL module, the front turn signal
bulbs operate normally. When the park lamps or
the head lights are on, the DRL removes voltage from
the front turn bulbs.
Fog Lights Circuit Description (Domestic)
With the Headlamp Swithin the HEAD or PARK
position, voltage is applied to one side of the Fog
Lamp Switch. When the Fog Lamp Switch is closed,
voltage is applied to one side of the Fog Lamp
Relay Coil, energizing the relay (the other side of the
coil is grounded through the HI Beam Filament of
the Headlamps).
When energized, the normally open contacts of the
Fog Lamp Relay close, allowing voltage to be applied
to the Fog Lamps.
When the HI Beams are activated, ground is removed
to one side of the Fog Lamp Relay Coil, de-energizing
the relay and turning off the Fog Lamps.