Revealed: How to solve a faulty Mercedes C220D SOS button

Buying a new vehicle is always a nervy experience, especially when the car is second-hand. 

But imagine buying a Mercedes only to find one of the key safety features is faulty. It’s enough to give you heart palpitations just thinking about it. 

When Mrs D bought her Mercedes C220D, its SOS button was permanently lit up, meaning she couldn’t use it if she ever had an accident. As it wasn’t working correctly, it put Mrs D’s safety at risk. 

To make matters worse, Mrs D had already visited another garage, but they couldn’t help solve the problem. Talk about a nightmare. 

Thankfully, she visited our Mercedes specialists at Fergies for a solution to her vehicle’s fault.

What we found

During our initial inspection of the C220D, our Mercedes experts used their experience, knowledge and the Mercedes manufacturer information to visually check over the vehicle for obvious causes. 

As your local Mercedes specialist we have access to the same information as the main Mercedes dealerships. You get dealership-level servicing for better than dealer value. 

It was clear the issue wasn’t surface level and needed a thorough inspection to identify the root cause of the problem. Our Mercedes experts suspected the vehicle’s manufacturer information and technical data could provide insight into the cause of the fault. This is something other garages might not have access to. But as Mercedes specialists, we do.  

Diagnosing the problem

Our Mercedes experts performed a comprehensive fault code analysis which gave the message ‘VIN not present fault code stored’. This is often caused due to a number of reasons, but I’ll leave those for another time. 

While the fault scan didn’t give much away, it didn’t phase our Mercedes technicians, as they knew what to do next. 

Using the onboard system data, the SOS button was pressed to confirm the control module was receiving the signal. It appeared the button was registering with the control module, ruling out a common fault.

At Fergies, our Mercedes experts use a 15-step diagnostic process to get to the bottom of any fault, allowing us to leave no stone unturned. You get a quality first-time fix no matter what the issue is, saving you time, money and stress. 

Once the SOS button was confirmed to be registering, it led our specialists to consult the Mercedes technical service information for any known causes. 

As an approved independent Mercedes garage, the Mercedes technical information we use is the same as the main Mercedes dealerships. This allows us to provide you with dealership-level care for better than dealership value. After consulting the information, we discovered a known software corruption issue which causes the SOS button to remain on when it shouldn’t. 

Eureka! Now the SOS button’s fault had been identified, our Mercedes experts could get Mrs D back on the road. 

Fixing the Mercedes

Now our specialists had a possible cause of the fault; they called Mrs D to discuss updating her vehicle’s software. 

At Fergies, you’re always kept informed from the minute you enter our garage. We only begin working on your vehicle after you give us the go-ahead.  Once Mrs D agreed to the proposed work, our technicians began updating the C220D’s software. And carried out a ‘teaching-in’ process to configure the SOS button. It might be technical, but it’s where our Mercedes specialists excel. 

Do you know what happened when we fired up Mrs D’s vehicle? 

The SOS button was no longer activated and worked only when pressed. Our technicians tested the button several times, and performed a road test to ensure everything was working as it should before we handed the keys back. 

Mrs D was pleased to have her Mercedes C220D in full working condition. And she was even happier to have her vehicle back the same day she dropped it off. You wouldn’t get service like that at the main Mercedes dealership. 

At Fergies, you always get better value than the main Mercedes dealer, while saving time and stress. 

Summary  

When Mrs D bought her Mercedes C220D, it had an annoying SOS button fault which rendered the button useless. While it didn’t affect the vehicle’s performance, it’s an important safety feature and without it Mrs D’s safety is at risk. 

To fix the issue, Mrs D took her vehicle to another garage, but they were unable to help with the problem. Luckily, she contacted our Mercedes experts at Fergies. 

Our specialists booked her vehicle during the same week she rang. Which is unheard of at the main Mercedes dealership. After thorough testing, using the Mercedes manufacturer information, and our 15-step diagnostic process, we discovered the fault…

It was a little-known software corruption issue. 

Thankfully our experts had encountered a similar issue before and knew what to do. The C220D’s software was updated and “taught-in” ensuring it worked precisely how it should.  Once the update was finished, Mrs D’s Mercedes ran like new with a fully working SOS button. 

Mrs D was over the moon to have her C220D back in working condition on the same day she’d dropped it off. And she was even happier when she got the bill. 

Got an issue with your Mercedes? Our Mercedes specialists would love to help. 

Call us on 01635 903172 and book your Mercedes check-up. 

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