What Size Bulbs Does a 2004 Cadillac CTS Use?
Correct headlight, fog light, and tail light bulb sizes. Sourced from OEM catalog data.
Installation Difficulty
Easy (Plug and Play)
Est. Replacement Cost
$50 - $150 (HID System)
What Lighting System Does the 2004 Cadillac CTS Have?
The 2004 Cadillac CTS features an extensive lighting system with 13 bulb positions. It uses factory HID/Xenon technology with D1S projector headlights. The CTS has been available from 2003 to 2019, and the 2004 model falls in the early-generation years.
Can You Put LED Bulbs in a 2004 Cadillac CTS?
The 2004 Cadillac CTS comes equipped with factory D1S HID/Xenon headlights. These already produce significantly more light than halogen bulbs, so upgrading is generally unnecessary. When your HID bulbs burn out, replace them with OEM-spec D1S HID bulbs to maintain the correct color temperature and beam pattern. Avoid cheap aftermarket HID bulbs as they can produce incorrect beam patterns and blind oncoming drivers. Your fog lights use a 9145 LED halogen bulb, which can be upgraded to LED for a whiter color match with your HID headlights.
How to Replace Bulbs on a 2004 Cadillac CTS
To remove the headlight bulb, disconnect the wiring harness, then twist the bulb counter-clockwise and pull it straight out of the housing. Older model years like the 2004 CTS typically offer easy access to the headlight bulbs from behind the headlight assembly under the hood. Most owners can complete the swap in under 10 minutes per side. HID headlights operate at high voltage. Always disconnect the battery before working on the headlight assembly. Never touch the HID ballast while the headlights are on, and handle the D1S capsule with gloves to avoid oil contamination. The fog lights are accessed from underneath the front bumper. You may need to remove a few plastic clips or screws from the fender liner to reach the 9145 LED fog light socket.
Full Upgrade Bundle
Upgrade All 13 Positions at Once
2004 Cadillac CTS Complete Bulb Size Chart
| Position | Bulb Size | Shop |
|---|---|---|
Low Beam | HID-D1S LED | Buy HID-D1S LED |
High Beam | 9005XS LED | Buy 9005XS LED |
Fog Light | 9145 LED | Buy 9145 LED |
Brake Light | PC175 LED | Buy PC175 LED |
Side Marker | 2825 LED | Buy 2825 LED |
Turn Signal Front | 2825 LED | Buy 2825 LED |
Turn Signal Rear | 3157K LED | Buy 3157K LED |
Dome Light | PC175 | Buy PC175 |
License Plate | 2825 | Buy 2825 |
Map Light | PC175 | Buy PC175 |
Parking Light | 2825 | Buy 2825 |
Reverse Light | 3157K | Buy 3157K |
Trunk Light | 211-2 | Buy 211-2 |
Want to upgrade everything at once?
Shop Complete LED Kit for 2004 Cadillac CTSHow Long Do 2004 Cadillac CTS Headlight Bulbs Last?
HID/Xenon headlights on the 2004 Cadillac CTS typically last 2,000 to 3,000 hours, or about 4 to 6 years of regular driving. As HID bulbs age, they shift color toward pink or purple, which is a clear sign that replacement is needed. Flickering on startup also indicates a worn bulb or failing ballast. At 22 years old, the original bulbs on your CTS are likely overdue for replacement. Even if they still illuminate, reduced brightness significantly impacts nighttime safety. When one headlight burns out, replace both sides at the same time. Bulbs from the same batch age at similar rates, and mismatched brightness is distracting to oncoming drivers.
What Bulbs Are Compatible with the 2004 Cadillac CTS?
Using the wrong bulb size can cause improper beam patterns that reduce your visibility and blind other drivers. It can also cause overheating inside the headlight housing, potentially warping the plastic lens or reflector. Always verify the bulb number before purchasing.
2004 Cadillac CTS Headlight FAQ
Did Cadillac CTS Bulb Sizes Change Over the Years?
Over its production run from 2003 to 2019, the Cadillac CTS has seen bulb size changes in the Low Beam, High Beam and Fog Light positions. The 2004 model uses the earlier bulb specification that was in place before the change around 2016. Always verify the exact bulb size for your specific 2004 model year using the chart above, as using the wrong size can result in poor fitment or reduced light output.
Other CTS Years
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These vehicles from other makes also use a HID-D1S LED low beam bulb: