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Mercedes-Benz C-Class: Why is My SRS Light On?

The air bags in your vehicle should function properly. If they don't, a warning light will appear. Here's what a solid SRS warning light could mean for your vehicle.

By Charlie Gaston - May 15, 2015

This article applies to the Mercedes-Benz w204 (2007-2014).

The supplemental restraint system (SRS) light in your vehicle will illuminate whenever there is a problem with your air bags or seat belt fasteners. Look for a solid warning light on your dash to identify signs that one or both parts could be malfunctioning, or in need of repair. This article will explain the likely culprits that could be triggering the warning light in your vehicle, and the actions you should take to remedy the problem. In many cases, this is a simple repair. However, you may need to seek help from a professional mechanic or Mercedes-Benz dealer if replacement parts are needed.

Materials Needed

  • Warranty (optional)
  • OBD-II scanner
  • Voltmeter

Option 1 – Check for trouble codes

You might be dealing with a malfunctioning air bag or seat belt fastener, but you'll need to check to determine which of the two is the actual culprit. To check for trouble codes, you'll need an on-board diagnostics scanner (OBD-II), which can be pricey if you do not own one already. Some auto parts stores loan these out, or will use theirs to retrieve any stored trouble codes on your vehicle for free.

  • Hook up the scanner to the Data Link Connector, which is located near the steering wheel.
  • Determine which trouble codes apply to your vehicle, and then have the necessary service work done.
  • Clear out the trouble codes once the repair work is complete.
    Figure 1. This is an OBD scanner.

Pro Tip

If you do not own an OBD-II scanner, it is recommended heading over to your local Mercedes-Benz dealer in lieu of purchasing one. Many dealers will run diagnostics on your C-Class for free. However, you may need to agree to have any needed service or repair done at their facility.

Option 2 – Replace seat belts

Set up an appointment to have your seat belts replaced. They might be malfunctioning due to a weak locking mechanism. Seat belts carry a limited warranty, so contact your local Mercedes-Benz dealer to set up an appointment today.

  • A malfunctioning seat belt could cause the SRS light in your Mercedes-Benz C-Class to display on the dashboard. The same is true even if the air bags in your vehicle are safe to deploy in a crash.
  • If your C-Class is under warranty, the dealer will replace the malfunctioning seat belt(s) at no cost to you.
  • One telltale sign of a malfunctioning seat belt fastener is an SRS light that repeatedly displays and then disappears.
Figure 2. Your seat belts should function properly at all times.

Pro Tip

A malfunctioning seat belt fastener is a serious repair that needs to be done right away, so don't delay in making your service appointment.

Option 3 – Check air bags

Have your local Mercedes-Benz dealer check your air bags. They might be malfunctioning. Unfortunately, this is one of those repairs that should left to the professionals.

  • You never want the safety of your C-Class compromised.
  • Therefore, set up a service appointment to have your driver's side and passenger's side air bags inspected.
Figure 3. There are multiple air bags located within your vehicle.

Pro Tip

Never drive with malfunctioning air bags.

Option 4 – Check your battery

It might be dying. Some C-Class owners have reported the SRS warning light displays when the battery is low.

  • Check your battery to determine if it needs a charge, or needs to be replaced.
  • The easiest way to check your battery is using a voltmeter.
  • If you do not own a voltmeter, however, a quick visit to your Mercedes-Benz dealer or a local mechanic could be the solution.
  • Many garages will not charge a fee to determine if your battery is in good condition.
Figure 4. This is a multi-function voltmeter.

Pro Tip

Your battery should be between 12.4 and 12.7 volts.

Option 5 – Check occupancy sensor

Have your local Mercedes-Benz dealer check your occupancy sensor. It might be malfunctioning. If the passenger occupancy sensor in your seats is malfunctioning, you'll be looking at a hefty repair bill of approximately $3,800 including parts and labor.

  • The dealer will need to replace your seat cushion.
  • It is not recommended trying to "cheat" the system or attempting this repair on your own.

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