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Universal fiber optic loop (MOST bypass)
Female MOST loop for BMW, Mercedes-Benz, and other MOST vehicles. Bring back radio, sound, navigation voice, and Bluetooth, and clear the SOS light.
The M&P USA universal fiber optic loop is a female MOST bypass loop that plugs into the fiber optic connector of a MOST multimedia module in BMW and Mercedes-Benz vehicles, so you can bypass a failed module and bring back your radio, sound, navigation voice, and Bluetooth, and fix an SOS error light caused by a broken fiber optic ring.
Unlike many standard loops, it fits the factory connectors on the satellite receiver, amplifier, TCU, MULF, CD changer, and other modules without cutting or modification. Designed in-house, made in the USA, and backed by our lifetime warranty.
The short answer
- No sound, no radio, or an SOS light on a BMW or Mercedes? One failed MOST module can break the whole fiber optic ring. This loop closes it again.
- Fits 2006-2011 BMW (green fiber optic cables) and most 2006-2011 Mercedes (usually orange). 2012 and newer BMW: contact us before ordering.
- 1998-2005 Mercedes with D2B? Use our D2B fiber optic bypass loop instead.
- Plug and play: unplug a module, plug in the loop, test. Step-by-step help in our fiber optic bypass loop guide.
On this page
Why one bad module kills your sound
MOST (Media Oriented Systems Transport) is a fiber optic ring: light passes through every multimedia module in a loop. If one module fails, the ring breaks and you can lose radio, sound, navigation voice prompts, and Bluetooth, and get an SOS or emergency call warning across the whole car. Unplug a module, plug our universal fiber optic loop into its fiber optic connector, and the ring is complete again. The bypassed module stops working, but everything else comes back.
Is this the right universal fiber optic loop?
Use this universal fiber optic loop if your BMW, Mercedes-Benz, or other vehicle uses the MOST fiber optic network. In BMWs the fiber optic cables are green; in Mercedes they are usually orange.
- 1998-2005 Mercedes with the older D2B system: use our D2B fiber optic bypass loop instead.
- 2012 and newer BMW: most functions moved into one combined module (the “com box”), so contact us and we’ll help.
Not sure? Send us your year, make, model, and the symptoms and we’ll help you find the bad module.
Before you buy parts, enter your VIN in the NHTSA recall lookup to check for open safety recalls; recall repairs are free at a dealer.
What’s included
- 1 universal female MOST fiber optic loop, custom designed to plug into the male MOST connector on your vehicle’s multimedia modules.
- Why female only: to test or bypass a module you only need the female side. Loops sold as “pairs” include a male loop that doesn’t help with sound or SOS troubleshooting.
Specifications
| Item | Detail |
|---|---|
| Product | Universal fiber optic loop (MPUSA102) |
| Network type | MOST (Media Oriented Systems Transport) fiber optic ring |
| Connector | Universal female, plugs into the module’s male MOST connector |
| Fits | BMW, Mercedes-Benz, and other MOST vehicles |
| Common modules | Satellite receiver (SDARS), amplifier, TCU (Bluetooth/SOS), MULF, CD/DVD changer, navigation, video module, head unit |
| Installation | Plug and play, no cutting or modification |
| Not compatible with | 1998-2005 Mercedes D2B (use our D2B loop) |
| Warranty | Lifetime |
| Returns | 30 days |
| Made in | USA |
Universal fiber optic loop fitment
| Make | Years | Fiber cable color | Notes |
|---|---|---|---|
| BMW | 2006-2011 | Green | Plug and play |
| BMW | 2012 and newer | Green | Contact us before ordering |
| Mercedes-Benz | 2006-2011 (most models) | Orange | Plug and play |
| Mercedes-Benz | 1998-2005 (D2B) | Varies | Not this loop: use the D2B loop |
| Other MOST vehicles | Varies | Varies | Contact us to confirm |
Customer-reported vehicles include the BMW 1 Series, 3 Series (E90, E92), 5 Series (E60), 6 Series, M3, M5, and X5, and the Mercedes-Benz C-Class (including the C230, C250, and C300), E350, S550, and SL500. 1998-2005 Mercedes with D2B: use our D2B fiber optic bypass loop.
How to find and bypass the bad module
- 1Find the modules. In most BMWs and Mercedes, the multimedia modules sit in the trunk near the driver-side tail light, or under the center console or carpet panel. Look for the green (BMW) or orange (Mercedes) fiber optic cables.
- 2Turn the car off. Unplug the fiber optic connector from one module.
- 3Plug in the loop. Plug our universal fiber optic loop into the vehicle-side fiber optic connector you just removed, closing the ring without that module.
- 4Test. Turn the car on and check the radio, sound, and warning lights. If everything works, you’ve found the bad module. If not, move the loop to the next module and repeat.
- 5Leave it in or replace the module. You can leave the loop in place permanently, knowing that module’s feature won’t work, or replace the failed module later.
Component locations vary by model and options. Contact us and we’ll help you find them.
Why M&P USA
- Universal fit: our universal fiber optic loop uses a custom female connector that fits the factory MOST connectors standard loops often don’t fit without cutting.
- Lifetime warranty: if it ever fails, we replace it at no charge.
- Made and supported in the USA by a certified veteran-owned business. Questions before or after your order go to a real person through live chat or our contact form.
- 30-day returns: see our Return & Refund Policy.
Frequently asked questions
Why does my car have no sound or an SOS light?
MOST is a ring, so one failed module, often the satellite receiver, amplifier, or TCU, breaks the ring and can knock out radio, sound, Bluetooth, and navigation voice, and trigger an SOS or emergency call warning. Bypassing the failed module with the universal fiber optic loop restores the ring.
Will the universal fiber optic loop fit my BMW?
Yes for 2006-2011 BMWs with green fiber optic cables, including the 1, 3, 5, and 6 Series, M3, M5, and X5. For 2012 and newer BMWs, contact us before ordering.
Will it fit my Mercedes-Benz?
Yes for most 2006-2011 Mercedes with MOST (usually orange fiber optic cables), including C-Class, E-Class, S-Class, and SL models. For 1998-2005 Mercedes with the older D2B system, use our D2B loop.
How do I find which module is bad?
Unplug one module at a time and plug the loop into its connector. When the sound comes back, the module you just bypassed is the bad one.
Can I leave the loop in permanently?
Yes. The ring works normally with the loop in place; only the bypassed module’s feature (for example, satellite radio) won’t work.
Why female only and not a pair?
To test or bypass a module you only need the female loop. The male side sold in pairs doesn’t help with sound or SOS troubleshooting.
Need help finding the bad module?
Read the fiber optic guide or send us your year, make, model, and symptoms, and a real person will help you troubleshoot.
BMW and Mercedes-Benz names are used only to identify compatible vehicles. M&P USA is not affiliated with, endorsed by, or sponsored by BMW AG or Mercedes-Benz Group AG.
Love hearing this, Juan. That SOS malfunction message on the E60 drives a lot of owners crazy, and getting your AUX and CD back for the price of a loop is exactly why we make these. Enjoy the music!