In most 2015 Subaru Forester models, the rear brake/taillight uses a 3157 dual-filament bulb (P21/5W). Some markets or trims may use a different base, so always verify on your vehicle by inspecting the bulb or checking the owner’s manual.
For drivers and mechanics, the quickest way to confirm the exact bulb is to remove the current bulb and compare its base to standard replacements, or consult Subaru’s parts diagram for your specific market and trim. This article explains the typical bulb type, how to verify it, and how to replace it.
Common bulb types for the 2015 Forester
Before listing common options, note that the most widely used rear brake/taillight bulb for the 2015 Forester is the 3157 dual-filament. Some export or alternative trims may use a different base in similar-function bulbs, so confirmation is recommended.
- 3157 (P21/5W) dual-filament bulb for the rear brake and taillight on the majority of US-spec 2015 Foresters. This single bulb handles both the stop and tail lighting functions.
- 7443 (W21/5W) dual-filament alternative in certain markets or trims; base and socket can differ from 3157, so verify fit before purchasing.
- LED replacements available in 3157 dual-filament form, often marketed as 3157 LED bulbs; these may require CAN-bus adapters or resistors to prevent fault warnings on some vehicles.
When selecting a replacement, prioritize the correct base and voltage (12V) and ensure the new bulb is compatible with your vehicle’s electrical system to avoid dashboard bulb-out warnings.
How to replace the brake light
Replacing the brake light in a 2015 Forester is straightforward, but it requires accessing the rear light assembly from inside the cargo area and handling the bulb carefully to avoid damaging the lens or wiring.
- Open the cargo area and remove any coverings or panels that provide access to the rear taillight assembly.
- Locate the brake/taillight socket. Turn the bulb socket counterclockwise to release it from the housing.
- Pull the old bulb straight out of the socket. Note the base for an exact replacement (3157, 7443, etc.).
- Insert the new bulb into the socket and push it in firmly, then twist the socket back into the housing until it locks.
- Test the brake light by pressing the brake pedal with the taillights illuminated to confirm proper operation before reassembling the panels.
If the new bulb doesn’t illuminate, re-check the bulb orientation, socket connection, or fuses. In some cases, low-impedance LED replacements may require CAN-bus adapters to prevent error messages.
Market-specific notes
Subaru’s 2015 Forester configurations can vary by market and trim. The 3157 bulb is the most common option for North American models, while some European or other-market variants may use a 7443-based setup. Always double-check with your vehicle’s manual or a Subaru parts diagram for your exact VIN and region.
In any case, carrying a spare 3157 (and a 7443, if you know your model uses it) can save time on the road, and opting for a CAN-bus-compatible LED can be worthwhile if you’re upgrading for brightness or longevity.
Summary
The 2015 Subaru Forester most often uses a 3157 dual-filament bulb (P21/5W) for the rear brake/taillight, with some markets or trims using a 7443 alternative. Verify by inspecting the existing bulb or consulting the owner’s manual. Replacement steps are straightforward: access the taillight assembly, remove and replace the bulb, then test the circuit. For upgrades to LEDs, ensure compatibility with CAN-bus systems to avoid warnings.