How to Solve Engine Performance & Climate Control Faults in Mercedes E – Class 

Executive cars are a class apart when it comes the luxury, performance and comfort. But you can take the executive aspect a bit further when Mercedes is concerned. The German automotive manufacturer does not mess around when it comes to producing quality luxury vehicles. They have done it for many years in the past, they continue to do so with the same motivation and fervour as before. 

Mercedes E Class vehicles have a touch of perfection and a quality standard that even its rivals fall short of matching. Such is the brilliance of work that goes on at their factories. 

So, it only comes as a surprise if someone comes to our Mercedes garage, complaining about issues with their E Class vehicle. 

One such client came to the Garden City Garage, complaining about the climate control system and the loss of performance in their Mercedes E – Class.  

Ms L complained about the Engine Management Light (EML) on the dash and the air conditioning system in her vehicle not working. Our Mercedes specialist, Thomas, listened intently to her complaints while trying to understand the relationship between the two apparently unrelated faults. 

Perhaps, there was no correlation between the two issues. Our Mercedes technician had to be completely sure and for that he started with the verification phase, followed by the diagnosis.  

Faults Found

Thomas had a very difficult job of understanding the client’s complaints and matching them with the issues in the vehicle. He had to get an idea before attempting the diagnosis. 

Luckily, Ms L could easily explain the problems she faced in her Mercedes E – Class vehicle and Thomas was able to make a mental map using that information.  

Our Mercedes specialist confirmed that there was an EML warning in the car and the A/C was also not working as Ms L had described. 

The client further said that she had visited another Mercedes garage that had scanned the E Class vehicle and diagnosed a blocked Diesel particulate filter (DPF). We couldn’t be sure about all this just by performing a visual inspection. So, our Mercedes specialist initiated the extremely helpful 15-step diagnostic procedure.   

Diagnostic Procedure   

All the technicians working at the Garden City Garage use the 15-step diagnostic process to achieve accurate results in less time. 

Thomas used the same diagnostic process to make sense of the issues plaguing Ms L’s Mercedes. 

The first step on his to-do list was to perform a full-body vehicle scan. Our Mercedes specialist used the Mercedes dealer-specific diagnostic tool to scan the car and found the following error codes on the system: 

• P244A00 – Differential Pressure in the Particulate Filter Too Low
• B107A15 – Short To Ground / Positive on Refrigerant Pressure Sensor  

The codes showed Thomas the exact location of the problem area. He could now use this new information and attempt to solve the issue. 

But before starting, our Mercedes specialist took the car out for a test drive and tested the apparent lack of performance. At the same time, he checked the A/C function and confirmed both issues to be affecting the vehicle. 

Once the test run was complete and the fault code scan turned up interesting results, the next step was to perform a physical back pressure test on the vehicle’s exhaust system. Our Mercedes expert tested the pressure and found no irregularities in the system. 

He later compared the readings from the sensor and again found nothing out of the ordinary. 

By now many technicians would have given up, but Thomas is in another league. That’s why he used an oscilloscope (not something you typically expect to find in garages) and scoped the sensor while also checking the wiring. 

It turned out that the signal was irregular at the ECU when the wiring was manipulated. 

The result was quite interesting, so our technician investigated the Mercedes technical information that Garden City Garage have access to as an approved independent Mercedes repairer – it’s the same technical information provided to the main dealers by Mercedes Benz. Finally, after looking for a while, Thomas found the perfect fix for this kind of issue  – the fix involved replacing the sensor and repairing the wiring loom using a genuine Mercedes repair kit. 

Once that was done and dusted, our Mercedes expert moved on to diagnose the climate control issue plaguing this E Class. 

For the A/C, our Mercedes specialist tested the entire system and measured the pressure sensor readings. There was something off, so Thomas looked at the wiring to confirm there were no issues with signal delivery. Luckily, all was good except for the pressure sensor which had failed. So, our Mercedes technician bypassed the sensor and tested the system again. It was working fine, which confirmed Thomas’s initial diagnosis. 

Now, the only thing left to do was employ the solution and hand over the car back to Ms L.  

Solving The Problem  

The first part of the solution was quite complex and it meant that our Mercedes technician had to consult the wiring diagrams and repair the wing harness leading into the DPF sensor. So, without wasting a minute of his time, Thomas started carefully repairing the wiring harness. 

Once that was done and dusted, our Mercedes specialist could replace the DPF pressure sensor and complete the first phase of the repair. 

Next up, was the climate control system, which was a quick and straightforward replacement for our Mercedes technician. All Thomas had to do was locate the sensor and replace it with a new one. When he was done with both these things, our Mercedes specialist took the car on a test run and approved the repair work to be complete.  

Finally, our team called the customer and gave her the good news about her 2010 Mercedes E Class. 

Summary 

A distressed Ms L visited our Mercedes garage complaining about two issues in her vehicle. She could see an Engine Management Light warning in the dash and the A/C was also not working, even though the car had ample refrigerant.  

Our Mercedes specialist used his knowledge, specialist skills, and access to Mercedes technical information along with the 15-step diagnostic procedure to find out the underlying issue in Ms L’s Mercedes. 

It turned out that the DPF sensor and the A/C pressure sensor had malfunctioned. On top of that, the DPF wiring leading in and out of the sensor was also affected. Our Mercedes specialist had to solve both issues.   

If you are looking for a Mercedes garage that offers value for money, while also providing you with the same service as a Mercedes Benz dealer, look no further than the Garden City Garage. You can contact us on 01639 320034  to learn more about our services. 

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