Mercedes AdBlue Fault

One moment your vehicle is running perfectly, the next you’ve pulled over and are frantically searching for “Mercedes AdBlue fault fix near me”. Engine light illuminated. AdBlue warning sitting alongside it. The questions start flooding in: “Is it still safe to drive?”, “How much is this going to cost?”, “Do I have to take it to a Mercedes dealer?”

Quick answer: no, you don’t. At Shires Garage Auto Services here in Langport, we’ve seen these issues before, and we can put them right without the main dealer prices or long waiting lists.

Recently, a Mercedes M-Class was booked in with us facing this exact scenario. Instead of being stuck with costly repairs and frustrating delays, the client received a full first-time fix plus their scheduled Mercedes B1 Service, all under one roof.

Sounds good? Keep reading to see exactly how we made it happen, and why choosing an independent Mercedes specialist can save you stress, time, and money.

What We Found: Two Warning Lights, A Bigger Underlying Problem

When the Mercedes M-Class arrived at Shires Garage Auto Services, it was originally due just for its Mercedes B1 Service. However, the owner had contacted us before the appointment to let us know both the engine management light and an AdBlue system fault light had appeared days earlier.

Definitely not something to ignore.

Those warning lights are serious indicators that something is amiss, and if left unresolved, can lead to much larger problems. You could end up with soaring emissions levels, or even the vehicle refusing to start.

With this in mind, we knew this wasn’t going to be a straightforward service. AdBlue system issues, although not rare, are concerning and need addressing. Faults here can arise from problems within the tank itself, failing sensors, wiring defects, or software glitches, and they do not resolve themselves.

Understanding AdBlue: Why It Matters for Your Mercedes

AdBlue is a clear, odourless liquid, composed of purified water and urea. It has a dedicated tank, usually distinguishable by a blue cap, positioned either next to your diesel filler cap, inside the boot, or beneath the bonnet.

In modern diesel vehicles, including the Mercedes M-Class, AdBlue is injected into the exhaust system. Its purpose? To break down harmful nitrogen oxides in the emissions into harmless nitrogen and steam, ensuring the vehicle meets strict Euro 6 emissions regulations. Almost all diesel models manufactured post-2015 rely on AdBlue technology.

If your Mercedes runs low on AdBlue, or if a fault occurs within the system, dashboard warnings typically appear.

Unsure about your AdBlue levels? Experiencing a fault? Don’t hesitate, call us today at 01458 250570.

Diagnosing the Fault: What Was Triggering the Mercedes AdBlue Issue?

With the M-Class in the workshop and the scheduled B1 service underway, we commenced a thorough diagnostic investigation to get to the root of the AdBlue problem. No guesswork. No cutting corners. Just methodical, professional diagnostics.

After conducting a comprehensive system scan, two critical fault codes were flagged:

• 205B98 – AdBlue temperature sensor malfunction
  
• 205C15 – Sensor short to ground
  

These codes might not mean much to most drivers, but to our experienced Mercedes specialists, they pointed directly to trouble within the AdBlue system. The readings indicated abnormally low temperatures and an electrical fault.

At first glance, it looked like a defective sensor or an issue within the AdBlue tank itself.

But experienced technicians know better than to jump to conclusions.

We pressed on with a deeper assessment, rechecking wiring inputs and ensuring no obvious electrical faults were missed. While early indicators pointed towards component failure, our extensive diagnostic process suggested there might be something more complex happening.

And that’s when we uncovered the real issue…

Further investigation revealed that it wasn’t the tank or sensor at fault, it was a software error producing misleading readings. Exactly the kind of fault you only catch with a rigorous, detailed diagnostic process and the right expertise.

With the culprit discovered, it was time to get to work. 

The Solution: Expertise Over Expensive Replacements

Once we identified the root cause, we contacted the customer to provide a clear explanation. No assumptions, no unnecessary parts replacement, just facts and a straightforward plan.

At Shires Garage Auto Services, we believe in complete transparency. We always seek full customer approval before proceeding, ensuring you stay in control of your vehicle and your costs.

With the client’s go-ahead, we installed the latest software update for the control unit. This update corrected the sensor readings and brought the AdBlue system back into full working order, without the need to replace the tank or sensor.

After applying the software update, we completed a full system check. Every aspect performed exactly as it should. No more dashboard warnings. No stored fault codes. No more worrying surprises.

Following the repair, we finished the scheduled B1 Service using genuine or equivalent high-quality parts, ensuring the vehicle’s performance, warranty, and compliance were all protected.

The outcome? A Mercedes M-Class running perfectly once again. Fault-free, serviced, and ready for the road.

The Outcome: One Visit, One Complete Solution

In this case, we were able to diagnose and resolve the AdBlue fault and complete the B1 service in just one appointment, saving our client from the hassle of multiple visits and unnecessary costs.

It’s a perfect example of the exceptional service you can expect when you trust Shires Garage Auto Services with your Mercedes. As your local independent Mercedes specialist in Langport, we deliver main dealer-level technical precision combined with the friendly, personalised service of a trusted local garage.

Every diagnosis and every repair is carried out with meticulous attention, technical accuracy, and a clear commitment to transparency.

If you’re based in Langport, Taunton or the surrounding areas, and you’re facing an AdBlue fault or need your next Mercedes B1 service, give us a call on 01458 250570. We’ll get you back on the road without the stress.

Why Mercedes Owners from Taunton and Langport Trust Shires Garage Auto Services:

• Main dealer knowledge, independent garage value
  
• Free courtesy car available to keep you moving
  
• Genuine or OEM-quality (1) parts for all services and repairs
  
• Every job is backed by a 12-month parts and labour guarantee
  
• Full clarity and approval on all work before we start

⭐ Our dedication to quality has earned us a {{average-rating}} star rating on Google from {{review-count}} delighted customers.

📞 Call us now on 01458 250570 to arrange your Mercedes appointment at Shires Garage Auto Services.

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(1) OEM stands for Original Equipment Manufacturer. When it comes to vehicle parts, this means the parts are made by the same company that produced the original parts for the vehicle manufacturer