Mercedes-Benz of Stevens Creek - 2047
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Mercedes-Benz of Stevens Creek - 2047

Mercedes-Benz C 300 SRS Malfunction - How To Troubleshoot and Fix

What Is the SRS?

Your Mercedes-Benz C 300’s SRS refers to your entire airbag system and all of the triggering sensors used to manage deployment in the event of a crash. This system includes airbags, your airbag control unit, emergency seat belt tensioners, belt force limiters, crash sensors, and front passenger seat occupancy sensors. All of these components work to pass data back to your module, with any defects noted using an error message in your instrument cluster.

SRS-equipped front airbags inflate when your airbag sensor assembly experiences high impact with a front-end crash. Seat belt tensioners and front airbags deploy to protect the head and chest from hitting your dashboard and windshield. Typically, airbags deploy when a 15 mph front collision force is detected.

SRS front airbags do not deploy in the event of side collisions, rear collisions, or vehicle rollover. However, if the front of your Mercedes-Benz C 300’s absorbs enough impact, they are likely to deploy. Note — once deployed, airbags cannot be reused. With each deployment, a combustible mix of sodium azide explodes within, converting to nitrogen gas and pressurizing the airbag to full “pop,” so the effect is irreversible. Airbag resetting is usually managed by a licensed Mercedes-Benz technician.

It is also important to note that your Mercedes-Benz C 300’s SRS is self-managing. Every time you turn on your Mercedes-Benz C 300, it will self-diagnose your SRS to determine if all sensors are working as needed. If sensors are defective, an airbag warning light will flash on your dashboard, indicating it may be time for troubleshooting and replacement.

Another important component of your SRS are airbag occupant sensors. They are strategically placed in the passenger seat and detects when a passenger is present by sensing weight, allowing the airbag control module to fire the airbags on that side. In the event of a defective airbag occupant sensor, your airbag or SRS warning light will light up on your instrumental cluster, staying on for roughly five seconds after turning the engine on.


Where Is the C 300 SRS Location?

Your Mercedes-Benz C 300’s SRS location is located beneath your center console. Note, this location is not exclusive to all vehicles. Airbag control modules in other vehicles could also be found below your center console, dashboard, or the driver seat.


Causes That Result In An SRS Malfunction on a Mercedes-Benz C 300?

Symptoms of a defective airbag control module are most notably a defective passenger seat occupancy sensor, low electrical system voltage, damaged door wire contracts, or damaged impact sensors.

Any of these conditions will activate a dashboard airbag (SRS) warning light that illuminates a small airbag or seat belt icon, indicating a potential issue with your sensors or airbag control system. Another cause to malfunction include damaged wires in the steering column, which may require dismounting and replacing a section of the wiring harness that connects to your dashboard.


Fixing Your Mercedes-Benz C 300 SRS

SRS airbag lights do not reset after activating. They need to be manually reset using an airbag scanner. Although “read and reset” scanners are available for purchase, we recommend taking all Mercedes-Benz C 300 SRS-related issues to your local certified Mercedes-Benz technician for a thorough inspection. Any applicable replacement parts can also be shopped on the Mercedes-Benz national store.

Another area to look at are airbags and seat belts. Airbags and seat belts have a series of electrical connectors with harness wiring plugs that could cause injury if not handled properly. Replacing a defective SRS involves disconnecting your SRS’s battery and removal of multiple components to diagnose and replace the system if needed. Certificated Mercedes-Benz technicians and dealerships are also able to reset your SRS with dedicated software that is not usually accessible or easily managed by regular drivers.

Fixing C 300 SRS is not a straightforward process although the Mercedes National store can offer you the products necessary to repair it. In terms of repair frequency, airbag occupant sensors may never need to be replaced since they are not used as much. In case they need repair, look to a certified Mercedes-Benz technician who can disconnect the battery/sensor, and install a new sensor with all of the appropriate reset codes and testing.