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Loss of Performance – Getting to the Root Cause

As a German Vehicle Specialist, we are regularly contacted by clients who are trying to fix and maintain their BMW/ Audi / Mercedes Benz.  Especially when they are not able or do not want to take it to a main dealer.

This is what happened recently with a Thatcham client, Mr Williams, and his 2006 Mercedes Benz CLS320.  

The initial complaint from the client was a lack of boost from the engine.  The car was almost undrivable and that was not what he expected from his luxury vehicle.  A ‘Design Icon’ is what Mercedes call the CLS Coupe… so when it’s not working, it’s disappointing.

Mr Williams advised that he had taken the car previously to a couple of other garages, including the main Mercedes dealer and no one had been able to diagnose the problem with the engine performance.  So, when he came to us as Mercedes specialists, his expectations were mixed… he was hoping we could fix his car but having been let down previously, he was apprehensive.

So after the client called and explained the problem, we booked his Mercedes straight in for a full diagnostic appointment.  A full appointment will give us the time to use our expertise and knowledge, as well as our specialist dealer equipment to get this client back on the road.

Starting with error codes

After the initial visual inspection of the car, we hooked the car up to the Fergie’s in-house system and discovered 6 Mercedes Benz error codes. 6!!

The error codes and their meanings were:

  • P2626 – Soot content of DPF (Diesel Particulate Filter) too high
  • P2530 – Inlet port shut off motor short to ground
  • P2527 – EGR (Exhaust Gas Recirculation) positioner short to ground
  • P2514 – Vent line heater short to ground
  • P2526 – Charge pressure positioner short to ground
  • P2376 – Throttle valve actuator – Voltage low

What does it all mean?

DPF – Diesel Particulate Filter is a filter which works to regulate the level of soot in the engine/exhaust system.  The filter works on passive and active regeneration, which needs the car to either be driven at prolonged high speed to get the passive regen kicking in, or if the filter has a soot content of more than 45% the active regen will start to clear the filter.  Both processes require the engine to heat up in order to burn off the additional particles and clean the filters.

EGR – Exhaust Gas Recirculation valve is set up to reduce the exhaust emissions on the vehicle.  It controls emissions by lowering oxygen concentrations in the combustion chamber.

So as both of these faults are pointing us towards the engine soot and combustion, we now can start the full diagnosis of the engine following our 15-step diagnostic process.

Now let’s start the fix

Our expert Mercedes technician started with checking the wiring diagram of the engine.  The technicians have enough experience to know they should check the wiring and fuses first as a precaution.

Having found that most of the components are all fused from the same fuse, they replaced the fuse before anything else to eliminate some of the error codes straight away.  Easy, quick fix.

Then with the remaining Mercedes Error codes, they went on to inspect the turbocharger and found a noticeable impact to the impeller (A rotor within the engine used to increase the pressure and flow of fluid within the engine).  This impact was causing oil to leak into the actuator.

Luckily our Mercedes experts knew exactly what to do:

  • They replaced the turbocharger
  • Repaired the swirl flaps
  • Replaced the Swirl flap actuator

So, including the replaced fuse, the error codes were now fixed and the car was running as normal, giving us a happy, satisfied client.

The repair of the swirl flaps, rod and actuator saved the client from a full replacement of the intake manifold, saving the client a substantial amount of time and money.  We were able to turn the car around within 48 hours, for a tricky, complicated fix and giving the Mercedes CLS320 back to the client with a full diagnostic report advising that the car is fully repaired, road worthy and safe.

Doing this differently

At Fergies, our expert technicians work with luxury Mercedes Benz vehicles regularly, so we have a different approach to diagnosis and repair – 15 steps to be precise!  We work hard to get to the cause of the problem and get the repairs completed quickly and cost effectively.  

If you have any questions about your Mercedes (or any other German vehicle for that matter!), or would like to book a full diagnostic appointment, please contact us on 01635 226248 where one of our expert technicians will be happy to help.

The team at Fergies were awarded the UK Top Technician of the Year 2018, priding ourselves on our knowledge, experience and customer service.

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