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How to fix Mercedes A-Class Mechatronics fault

When you’re driving a luxury car like a Mercedes A-Class, you want it to be a smooth drive, right?

Unfortunately for Mr Hall, his A-Class had become a nightmare to drive. It was jerking all over the place and had issues changing gears.

To make matters worse, he’d only just bought the car.

Imagine buying a new car, only to find it doesn’t perform as well as you’d thought it would. It’s enough to leave a bitter taste in anyone’s mouth.

Plus, who knows what issues are lurking beneath the surface. The last thing Mr Hall wanted was to have an accident because of the problem.

Thinking the worst, he brought his Mercedes A-Class to our specialists at Fergies for a once over.

What we found

During the initial inspection, our expert technician took the Mercedes for a road test and confirmed the issues.

Our Mercedes specialist had suspicions about what was wrong but wanted to be 100% sure.

A fault code scan gave the following readings:

  •       056200 – Power supply circuit 87 undervoltage.
  •       051300 – Start enable not issued.

Now, these probably don’t mean much to you. But to our Mercedes specialist, it helped confirm there was an issue with the Mercedes A-Class gearbox.

Once our expert technician knew where to focus, he used the Mercedes technical wiring diagrams to better understand what was happening.

At Fergies, our technicians evaluate every vehicle using a 15-step diagnostic process. Doing so ensures we find the root cause quickly, saving you time, money, and stress.

Using the 15-step process and our Mercedes expert’s knowledge, we found the fault during Mr Hall’s first visit. This is something other garages might not have done.

Diagnosing the issue

During the 15-step diagnostic process, our Mercedes technician used the manufacturer’s wiring diagram to test the transmission power and grounding. No fault was found, which meant there was an internal issue with the transmission mechatronics unit.

The mechatronics unit converts your car’s electronic signals into hydraulic power inside your gearbox. When it fails, it can lead to an interruption between the engine and gearbox.

While the Mercedes still worked, having a faulty mechatronics unit can be dangerous. More often than not, it can force your car back into neutral gear. It’s the last thing you’d want to happen to you on the road, especially on a motorway.

Fixing the mechatronics malfunction

Now we knew the issue; our Mercedes technician could start fixing it.

Before we began any work, we called Mr Hall to discuss his options, and he agreed to have a new mechatronics unit fitted. We believe in keeping you updated at every stage and never start working on your vehicle without your consent.

At Fergies, we use only genuine Mercedes or high-grade parts to give your car the quality it needs. We sourced and ordered a new mechatronics unit for Mr Hall’s Mercedes A-Class.

Our Mercedes technician used the Xentrey Kit 4 Mercedes diagnostic and encoding tool during the installation to program the new unit.

Other garages might not have or understand this tool, leaving Mr Hall stuck with no fix for his Mercedes A-Class.

Luckily, our Mercedes specialists have the experience and skill to provide him with a first-time fix.

Once the new Mercedes mechatronics unit was fitted and programmed, Mr Hall’s A-Class was retested.

The vehicle’s fault codes had cleared, and the Mercedes drove smoother than ever. No more jerkiness and difficulty changing gears.

Mr Hall was pleased to have his Mercedes A-Class in working condition. He was even happier when we gave him the bill, which was less than the Mercedes dealership’s prices.

Fergies loves to give customers a dealership-level service without the price tag.


Mr Hall’s Mercedes A-Class didn’t drive as smoothly as expected. It was jerking, and he had trouble changing gears.

Thankfully, he decided to bring his A-Class to our Mercedes specialist at Fergies.

Our expert used a 15-step diagnostic process to identify the root cause of the problem quickly. His car needed a new mechatronics unit which we sourced, fitted, and encoded during his first visit.

The Mercedes A-Class ran like new after the mechatronics unit was fitted and all fault codes had cleared.

Mr Hall even managed to save money compared to what the Mercedes dealership would charge. Talk about a win-win situation.

If your Mercedes A-Class isn’t running as smoothly as it should, or you’re experiencing gearbox issues, call Fergies and speak with our experts.

Call us on 01635 778002 and book your Mercedes for a first-time fix and better value than the Mercedes dealership.

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