CTS 2003-2005

Exterior Lights 1

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Brake, Signal & Marker Lights



Removal & Installation
Front Turn Signal & Parking Lights

The front parking/turn signal lamps are located in the left and right side composite headlamp housings (GM also calls them headlamp capsules). The parking lamps can be operated any time using the headlamp switch. When a turn is signaled, the appropriate front parking lamp switches to signal a turn. The turn signals operate only with the ignition switch in the RUN position and will not operate during hazard flasher operation.

Look the job over carefully. On some vehicles, the parking and turn signal lamp bulbs can be replaced by simply twisting the socket free and replacing the bulb. On other vehicles, the lamp assembly must be removed.

  1. Open the hood.
  2.  
  3. If the parking/turn signal bulb can be accessed, twist the socket to free it from the lamp assembly and withdraw the socket and bulb assembly.
  4.  
  5. If the parking/turn signal bulb cannot be accessed, remove the lamp assembly. Twist the socket to free the locking tabs and withdraw the socket and bulb assembly. Some applications may use a locking tab that needs to be depressed so the socket can be rotated.
  6.  



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Fig. This parking lamp/turn signal socket has a locking tab that needs to be depressed to rotate the socket



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Fig. Depress the locking tab with your thumb, then rotate the socket to remove



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Fig. With the socket free, the bulb can be replaced



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Fig. Carefully push in the bulb and turn it counterclockwise to unlock it

High-Mount Brake Light

The high-mounted stoplamp is in the center of the rear window and lights whenever the brake pedal is depressed and the stoplamp switch is closed. The bulbs are accessed from inside the trunk.



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Fig. This Grand Prix had a slotted vent panel covering the high-mounted stoplamp assembly. Squeeze the ends to remove or install



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Fig. A quarter-turn removes the socket so the bulb can be serviced

  1. Open the trunk.
  2.  
  3. If equipped with a slotted vent panel, remove it from the access opening by squeezing the ends and pulling down.
  4.  
  5. Reach through the access opening and turn the bulb socket 1 / 4 -turn counterclockwise to remove the socket. Most applications will use two sockets/bulbs. Verify that the correct bulb is being replaced.
  6.  
  7. Replace the bulb as required.
  8.  

License Plate Lights

The license lamp(s) are located in the rear fascia license pocket or the trunk lid applique panel. The lamp(s) light whenever the headlamps or parking lamps are activated.

  1. If the lamp is mounted to the fascia panel:
    1. Remove the retaining screws.
    2.  
    3. Remove the socket and change the bulb.
    4.  

  2.  
  3. If the lamp is mounted to the trunk lid applique panel, perform the following:
    1. Open the trunk and locate the applique harness connector. Detach the connector.
    2.  
    3. Using a small flat-bladed prytool, remove the grommet at the trunk lid.
    4.  
    5. Remove the wing nuts from the applique panel.
    6.  
    7. Remove the applique panel from the trunk link.
    8.  
    9. Remove the light socket(s) and change the bulb(s).
    10.  

  4.  
  5. Installation is the reverse of the removal process.
  6.  



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Fig. Removing the license plate lamp retaining screws with a small socket wrench and a flexible extension



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Fig. Separate the license lamp from the rear panel



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Fig. With the license plate lamp removed, unplug the socket and change the bulb



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Fig. On some models, the license plate lamp and even back-up lamps are mounted in the trunk-mounted rear fascia panel, detachable by removing the inside fasteners

Rear Turn Signal, Brake & Parking Lights

The taillamps, stoplamps and rear turn signals lamps are all incorporated into the rear taillamps. The taillamps are lit whenever the parking lamps or headlamps are in operation. The rear turn signal lamps flash with the front turn signal lamps whenever a turn is indicated with the turn signal/headlamp dimmer switch. The stoplamps light whenever the brake pedal is depressed and the stoplamp switch is closed.



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Fig. The trim panel is likely held in place with retainers like this. Back out the screw to release tension on the pin legs and remove the fastener



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Fig. The taillamp is retained by plastic wingnuts



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Fig. Remove the plastic wing nuts from the taillamp housing



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Fig. Remove the taillamp housing from the vehicle to service the light bulbs

  1. Open the rear compartment (trunk).
  2.  
  3. If equipped, unhook the convenience net that stretches between the taillamps. It is attached to hooks molded into the plastic taillamp assembly retaining wingnuts. Loosen the rear compartment trim panel. It is retained by plastic pins with a screw in the center. Back out the screw to release any tension on the plastic pin legs, and pull the trim (thin carpet-like material) for access to the taillamps.
  4.  
  5. Remove the plastic taillamp assembly retaining wingnuts.
  6.  
  7. Remove the taillamp assembly from the vehicle and service the light bulbs as required.
  8.  
  9. Installation is the reverse of the removal process.
  10.  
  11. Test the lights for correct operation.
  12.  

Side Marker Lights

The side marker lights are located on the sides of the headlamp assemblies. These lamps will light when the headlamp or parking lights are ON. If the headlamp or parking lamps are OFF when a turn is signaled, the appropriate side marker lamp will flash in unison with the with the front turn signal lamp. If the headlamps or parking lamps are ON when a turn is signaled, the side marker lamp and the front turn signal lamp will flash alternately.

  1. On some applications, the marker lamp bulb socket can be accessed through the engine compartment or from under the front valence panel. On other applications, the headlamp assembly should be removed for access.
  2.  



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Fig. On some applications, the side marker bulb socket can be accessed through the engine compartment or from underneath



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Fig. On this application, the side marker bulb lamp is part of the headlamp assembly



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Fig. Twist the socket to unlock it and pull the bulb from the socket

  1. The side marker lamp socket simply twists to remove.
  2.  
  3. The bulb is a baseless bulb and just pulls out of the socket.
  4.  
  5. Inspect the socket. They are often subject to road splash, dirt and corrosion. Clean as required.
  6.  
  7. Install a new bulb and reassemble in the reverse order of removal.
  8.  

Testing
Brake & Turn Signals

Modern turn signals first came into general use in the United States in the 1950's. Testing the turn signal circuit can be done with a simple test light.

Fog & Driving Lights



The fog lamps are operated by a separate instrument panel mounted switch. The fog lamps will go off whenever the high-beam headlamps are turned on and when you return to low beam headlamps, the fog lamps will come on again. Most installation have provision for vertical (not horizontal) aim by an adjusting nut located on the rear of the fog lamp.

Installing Aftermarket Auxiliary Lights

GM states "Don't add anything electrical to your (vehicle) unless you check with your dealer first. Some electrical equipment can damage your vehicle and the damage won't be covered by your warranty. Some add-on electrical equipment can keep other components from working as they should."

Because of the extensive computer control of your W-Body vehicle, just "tapping in" to an electrical circuit could produce unforeseen problems, not the least of which is corrosion from where the wiring insulation has been compromised. Always consult with your dealer before adding any aftermarket equipment on your vehicle.

Removal & Installation


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Fig. Fog lamps are mounted under the bumper either in pockets in the bumper or on small brackets-Pontiac shown



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Fig. These fog lamps are mounted under the bumper on small brackets-Buick shown

  1. Detach the electrical connector from the rear of the lamp.
  2.  
  3. Remove the lamp mounting nuts.
  4.  
  5. Installation is the reverse of the removal process.
  6.  

 
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