Chevrolet Silverado / GMC Sierra. Service manual — part 2507

TAIL LAMP BULB REPLACEMENT (GMC)

Fig. 61: Tail Lamp Bulb Replacement (GMC)
Courtesy of GENERAL MOTORS CORP.

TAIL LAMP BULB REPLACEMENT (CHEVROLET)

locating pins in the body panel.

Callout

Component Name

Preliminary Procedure:
Remove the rear tail lamp. Refer to Tail Lamp Replacement (GMC) or Tail Lamp
Replacement (Chevrolet).

1

Park and Turn Signal Lamp Bulbs (Qty: 2)

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Fig. 62: Tail Lamp Bulb Replacement (Chevrolet)
Courtesy of GENERAL MOTORS CORP.

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

DESCRIPTION AND OPERATION

EXTERIOR LIGHTING SYSTEMS DESCRIPTION AND OPERATION

Exterior Lamps

The exterior lighting system consists of the following lamps:

The headlamps

The daytime running lamps (DRL)

The front fog lamps

The park, tail and marker lamps

The exterior courtesy lamps

The turn signal/hazard lamps

The stop lamps

The backup lamps

The cargo lamps

The roof beacon lamp (if equipped)

Headlamps

The headlamps may be turned on in 2 different ways. First, when the driver places the headlamp
switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch
placed in the AUTO position, for automatic lamp control (ALC). During ALC the headlamps will
be in DRL operation in daylight conditions, or headlamp operation in low light conditions.

Headlamp ON/OFF control is determined by the body control module (BCM) by a signal on the
headlamp switch on input circuit when the headlamp switch is in the HEAD position. When the
headlamp switch is in the AUTO position, the BCM determines headlamps ON/OFF by the
voltage from the ambient light sensor.

If the headlight switch is left in the ON position, the inadvertent power control feature will turn
off the headlights approximately 10 minutes after the ignition switch is turned to the OFF

Callout

Component Name

Preliminary Procedure:
Remove the rear tail lamp. Refer to Tail Lamp Replacement (GMC) or Tail Lamp
Replacement (Chevrolet).

1

Park and Turn Signal Lamp Bulb (Qty: 2)

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

position. If the driver places the headlight switch in the ON position after the ignition switch has
been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain on
until turned off or the battery runs dead.

The high beam indicator is illuminated when the instrument cluster receives a GMLAN serial data
message from the BCM that the high beams are illuminated.

High Beams

The high beam headlamps receive voltage from the headlamp high relay located in the underhood
fuse block. The BCM controls the relay on the headlamp high beam relay control circuit. High
beam control is determined by a signal on the headlamp dimmer switch signal circuit from the
multifunction switch. When the headlamp dimmer switch signal circuit is grounded, the BCM
grounds the headlamp high beam relay control circuit, illuminating the high beam headlamps. The
right and left high beam circuits are independent and are fused independently in the underhood
fuse block.

Low Beams

The low beam headlamps receive voltage from the headlamp low beam relay located in the
underhood fuse block. The BCM controls the relay on the headlamp low beam relay control
circuit. Low beam control is determined by a signal on the headlamp dimmer switch signal circuit
from the multifunction switch. When the headlamp dimmer switch signal circuit is open, the BCM
grounds the headlamp low beam relay control circuit, illuminating the low beam headlamps. The
right and left low beam circuits are independent are fused independently in the underhood fuse
block.

Daytime Running Lamps (DRL)

The DRL will only operate while the engine is running and the headlamp switch is in the AUTO
position. When these conditions have been met and the ambient light sensor indicates daytime
conditions, the DRL will illuminate. The ambient light sensor is a light sensitive transistor that
varies its voltage signal to the BCM in response to changes to the outside ambient light level.
When the BCM receives this signal it will either turn on the dedicated DRL on the X88, the low
beam headlamps only as DRL on the Z88, or the headlamps, park, and tail lamps for auto
headlamp operation in low light conditions. Any function or condition that turns on the headlights
will cancel the daytime running lamps operation. The DRL can be manually turned OFF by
activating the AHL/DRL switch in the headlamp switch. The AHL/DRL defeat switch sends a
ground signal through the DRL switch signal circuit to the BCM. The BCM then turns OFF the
DRL. When the AHL/DRL are manually turned OFF at the headlamp switch, the AHL/DRL will
default to ON with the next ignition cycle. With the headlight switch in the AUTO position, the
DRL will either be turned ON or OFF after an approximate 8 second delay, depending on

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado