What Size Bulbs Does a 2004 BMW 645ci Use?
Correct headlight, fog light, and tail light bulb sizes. Sourced from OEM catalog data.
Installation Difficulty
Hard (Tight clearances)
Est. Replacement Cost
$50 - $150 (HID System)
What Lighting System Does the 2004 BMW 645ci Have?
The 2004 BMW 645ci features an extensive lighting system with 12 bulb positions. It uses factory HID/Xenon technology with D2S projector headlights. The 645ci has been available from 2004 to 2005, and the 2004 model falls in the early-generation years. As a BMW vehicle, it uses a CANbus electrical system that monitors bulb status.
LED Flicker Warning
This vehicle (BMW) is known to use a CANbus system that checks for burnt-out bulbs. Installing standard LEDs may cause them to flicker or trigger a dashboard error.
We highly recommend using a CANbus decoder or "Anti-Flicker" resistors.
Can You Put LED Bulbs in a 2004 BMW 645ci?
The 2004 BMW 645ci comes equipped with factory D2S 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 D2S 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 9006 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 BMW 645ci
To remove the headlight bulb, disconnect the wiring harness, then twist the bulb counter-clockwise and pull it straight out of the housing. BMW vehicles are known for tight engine bay clearances around the headlight assembly. You may need to remove the air intake duct, battery cover, or wheel well liner to access the bulbs. Budget 30 to 45 minutes per side for your first replacement. 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 D2S 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 9006 LED fog light socket.
Full Upgrade Bundle
Upgrade All 13 Positions at Once
2004 BMW 645ci Complete Bulb Size Chart
| Position | Bulb Size | Shop |
|---|---|---|
Low Beam | HID-D2S LED | Buy HID-D2S LED |
High Beam | H7 LED | Buy H7 LED |
Fog Light | 9006 LED | Buy 9006 LED |
Brake Light | LED Bulb | Buy LED Bulb |
Side Marker | LED Bulb | Buy LED Bulb |
Turn Signal Front | 2827 LED | Buy 2827 LED |
Turn Signal Rear | 12496 LED | Buy 12496 LED |
Dome Light | 6418 | Buy 6418 |
License Plate | 2825 | Buy 2825 |
Map Light | 6486X | Buy 6486X |
Parking Light | N/A | Buy N/A |
Reverse Light | 7506 | Buy 7506 |
Trunk Light | 6418 | Buy 6418 |
Want to upgrade everything at once?
Shop Complete LED Kit for 2004 BMW 645ciHow Long Do 2004 BMW 645ci Headlight Bulbs Last?
HID/Xenon headlights on the 2004 BMW 645ci 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 645ci 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 BMW 645ci?
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 BMW 645ci Headlight FAQ
Did BMW 645ci Bulb Sizes Change Over the Years?
The BMW 645ci has maintained consistent bulb sizes across all model years from 2004 to 2005. The low beam has used a HID-D2S LED bulb throughout, which means replacement parts and LED upgrade kits are widely available and well-tested for this model. If you find a deal on bulbs for any 645ci year in this range, they will fit your 2004 model.
Other 645ci Years
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Other Vehicles That Use HID-D2S LED Bulbs
These vehicles from other makes also use a HID-D2S LED low beam bulb: