2025 GMC Acadia — Bulb Sizes (Headlight, Tail, Fog)

Quick reference

Notes:

• For North American 2025 GMC Acadia models, exterior lighting is generally full LED across trims. Some trims add dedicated LED fog lamps (AT4, Denali). If your vehicle differs (fleet/export), confirm with the VIN and owner’s manual.
• Where “n/a (sealed)” is listed, the service procedure replaces the assembly or service module rather than a replaceable bulb size.

LED vs halogen upgrade considerations

• Headlights: The 2025 Acadia uses factory LED projectors. There is no halogen bulb to swap; upgrading means replacing the entire headlamp assembly with a different OEM/aftermarket LED unit. Avoid “LED bulb” conversions—they won’t fit and can cause beam pattern and legal issues.
• Turn signals and DRLs: These are BCM‑controlled LEDs. If you change assemblies, no resistors are required. If you retrofit a custom incandescent/LED solution, you may trigger hyper‑flash or lamp‑out warnings; CANBUS‑compatible parts or BCM reprogramming may be required.
• Fog lights: On trims with LED fogs, they’re sealed modules. Aftermarket pods often require adapter brackets and error‑free harnesses.
• Interior: Most dome/map lights are LED modules. If you prefer a different color temperature or brightness, look for direct‑fit LED service modules, not generic bulbs.
• Electrical load and CANBUS: The Acadia monitors certain circuits. Using the wrong load or tapping wiring can set DTCs or cause flicker. Always use application‑specific harnesses/adapters.

How to replace each bulb (module)

• Headlight low/high (LED projector): These are part of the headlamp assembly. Replacement typically requires removing the front bumper cover, upper grille fasteners, and headlamp bolts, then disconnecting the multi‑pin connector. Aim/calibrate per OEM procedure after installation.
• Fog light (LED module): Access from below by removing the front lower splash shield or wheel‑liner fasteners. The module bolts to the fog bezel; unplug the connector and swap the unit.
• DRL: Integrated into the headlamp; service is by replacing the headlamp assembly. Some failures are driver‑board related—inspect for moisture before replacement.
• Front turn signal: Integrated into the headlamp; replace the headlamp assembly if inoperative. Verify BCM output and ground if both sides or multiple functions are out.
• Tail/brake/turn: These functions are within the tail lamp assemblies. Open the liftgate, remove access panels and lamp retaining screws, pull the lamp straight back to release alignment pins, disconnect the connector, and replace the assembly.
• Reverse light: Housed in the tail/liftgate lamp module (varies by trim). Service the corresponding LED lamp module or full assembly.
• License plate light: Use a plastic trim tool to release the lamp from the liftgate garnish. Unplug and replace the complete LED lamp module.
• Side markers: Front side marker is in the headlamp; rear side marker is in the tail lamp. Service by replacing the respective lamp assembly.
• Interior dome/map: Carefully pry the lens or overhead console trim (use a trim tool), unplug the LED board/module if it’s serviceable, and replace with a direct‑fit module. On non‑serviceable units, replace the entire lamp assembly.

Always disconnect the battery when working near airbag sensors/wiring and use dielectric grease on exterior connectors. If the vehicle has automatic headlamp leveling or front camera/lighting ADAS, perform required calibrations after headlamp replacement.

Common lighting issues for this generation

• Moisture/condensation inside headlamps or tail lamps leading to flicker or DRL failure; inspect vents and seals, replace assemblies if moisture persists.
• BCM‑related hyper‑flash after collision or accessory wiring—often resolved by correcting grounds or programming after parts replacement.
• Trailer wiring causing lamp‑out messages; use a powered module that isolates trailer load from the vehicle’s circuits.
• Broken tabs or misalignment after bumper service can affect headlight aim and adaptive high‑beam performance.
• Early LED module dimming due to heat—ensure cooling paths aren’t blocked by aftermarket grille inserts or covers.

If your Acadia appears to use a replaceable bulb in any position, verify by VIN and consult the service manual; regional/fleet variations exist.

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