Diesel Particulate Filter (DPF) Regeneration


In the case of both Mercedes and the VAG group (VW, Audi, Seat & Skoda) we offer a forced  DPF regeneration service. This diagnostic procedure is the manufacturer approved method of cleaning and renewing your DPF. By raising your exhaust temperature to a sufficient level to initiate the required ‘burn’ effect, your filter can be returned to a fully functioning state without the need to replace or remove the filter, maintaining your warranty and increasing your vehicles performance.

Understanding DPF’s

Modern diesel engines have become increasingly complex as they have become a viable alternative to petrol engines. Ireland has seen a huge increase in the levels of diesel car ownership over the past ten years. The increasing complexity and requirements to run them as ‘green’ as possible has lead to increased maintenance and repair costs. Many diesel vehicles are unwittingly not used correctly by customers, they normally require long high torque journey to run as efficiently as possible. Slow ‘stop-start’ city driving is unfortunately a common cause of issue with diesel engines. TrapOxclogged100_0933.jpg

A blocked filter will normally bring about poor engine performance, increased fuel consumption and most notably a constant engine management light. Unfortunately, DPF problems are commonly misdiagnosed due to a lack of understanding of these systems and the lack of the correct diagnostic software. Many garages will recommend a complete replaced costing thousands of euro whilst others may recommend by-passing the system altogether. The first option is excessively expensive, whilst the second is not recommended by any manufacturer.

  • What is a disel particulate filter?
    A diesel particulate filter (or DPF) is a device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine.
  • Does my car have a DPF?
    Most diesel cars sold from 2008 onwards will be fitted with the filter.
  • How do I know my DPF is blocked?
    An engine management light along with poor engine performance may signal a blocked filter
  • Is it harmful to continue driving?
    Most vehicle will drop into a ‘limp-mode’ restricting the ability of the engine. Prolonged used in this state can lead to extensive vehicle damage as the engine is operating under undue stress. Pressure sensors, catalytic converters and turbochargers can all be damaged as a result of blocked filters.
  • How does a regeneration work?
    A passive regeneration can occur without drivers even noticing in regular day-to-day driving. As the vehicle fills predetermined conditions such as engine speed and exhaust temperature, the system itself will attempt to clean the DPF to maintain it’s efficiency. Problems arise when these conditions are not met (often as a result of city driving) and this is when a forced regeneration is required.

Changing combination switch W203 C-Class Mercedes 2001)


A common fault found in many W203 Mercedes-Benz C-Class models is a failing combination switch. This is evident by the stalk not returning to the neutral position after selecting either a left or right run. The switch will either 1) continue in the (left/right) selected position after the steering wheel has been returned to the straight ahead position following a turn or 2) the switch will not stay in the selected position and as such needs to be held in place during indicating. Here is a short explanation of how to replace this part.

Please note that not all models are identical to the below, this job was carried out on a 2001 C220 CDI, there are numerous different part numbers and the process varies slightly also.

  1. Ensure the steering wheel is set in the straight ahead position and the key is removed from the ignition. Remove the steering wheel centre airbag unit by loosening the two T30 Torx bolts mounted at either side of the wheel towards the back.

T30 Torx head

2. Once loosened this will allow the airbag unit to easily pull forward, giving access to the yellow and green airbag plugs as well as a steering wheel control plug (black). To remove the airbag plugs, simply prise the centre pins up and then prise the whole plus from the wheel unit.


Airbag connectors

3. You now have access to remove the steering wheel itself, the centre nut will need to be removed using a heavy rachet or Allen key adaptor as it requires a lot of force to remove. Ensure when the wheel is coming of to note the notches on the splines which allow you to locate the centre for refitting. Feed the airbag wires through the gap.


Remove steering wheel

4. If your steering wheel is set in the correct position, you will be able to see the below three Phillips head screws which hold the steering angle sensor in place. Remove these screws and ensure it does not spin away from its relevant position when left aside. If you can not see these screws, then the wheel is in the wrong location. If you reattach the wheel to move to the right location without firstly reattaching the airbag unit, you will enter an SRS fault in the ECU which will need to be erased using a Mercedes STAR Diagnosis machine.


Clock spring/Steering angle sensor

5. You will now see the combination switch which we are trying to reach, remove the three T25 screws visible and pull both the unit (and the cruise control unit, if fitted)out of the column. Unplug the three connections and remove from the vehicle.


T30 Torx head

6. Faulty unit


T30 Torx head

7. SRS faults, if you do not have access to a diagnostic machine to clear these faults, ensure you do not turn the key on whilst the airbag unit is disconnected.


T30 Torx head

8. Install in reverse order

If you have an issue like this and would like to use our expert service please don’t hesitate to contact us.

If this is of assistance to you, let us know in the comments below.

1995 W202 Mercedes C180 Central Locking Issue

• The red light on the key still operates, therefore we know that the batteries are still operational
• When the key button is pressed within the distance of the receiver (in this case, the receiver is located in the rear view mirror but it may also be located on the outside of the door handle) we see either a repeating flashing green or red light, indicating the activation or deactivation of the system immobilizer.
• An alternating green-to-red light indicates that the remote is out of sync and will need to be reprogrammed.
• There is no movement from the door locks at all and no noises apparent from the central locking pump

• Test the fuse (in this case Fuse 42 under the bonnet is responsible for the central locking system as well as fuse 3 in the boot section under the mat)
• Ensure we are receiving power at the central locking pump motor through the Red wire and a ground through the Brown wire. We know there is no power issue
• Now remove the central locking pump to test that there are no issues with the vacuum lines which operate the locks. You’ll need access to an vacuum gauge that can output roughly 3 psi. Connect the gauge to the yellow line which feeds into the central locking unit. Operate the locks in both directions and ensure all locks open and close correctly and hold their positions
• If all of the above tests have been successful, then it’s safe to assume that we are looking at a faulty central locking unit.
• When you have the unit removed from the car, you will be able to take a much closer look at the internal of it and see if there is anything which can be repaired. The unit consists of a motor with vacuum line and a circuit.
• To test the motor simply apply a 12V feed and a ground to either side of the contacts and it should run consistently
• The circuit board was the source of our problems in this example and although the broken joint was visible to us, it was not repairable. However, this is not to say that other boards may not be repairable. Inspect the board under microscope if necessary and if possible attempt to repair. After 20 years, this unit had seen better days so a replacement was sourced which immediately rectified the system and had the central locking running again.


Let us know of your attempts in the comments!

Protecting your car warranty

A statement we hear quite often from our customers is that they would have brought their cars to us sooner, but they had to use the brand specific garages to protect the warranties on their new vehicles. This is a common misconception. For obvious reasons consumers will be drawn towards branded garages however under EU law, their vehicles are fully covered under all warranties as long as the service provided by any workshop is carried out by a qualified mechanic using the appropriate genuine replacement parts.

The incentive for consumers here comes in many forms. Firstly, the reduction in cost from using smaller independent garages should be noticeable in many circumstances. Secondly, you are able to develop a much stronger relationship with smaller local garages who rely on your business far more than larger worldwide brands (it’s always handy to have a direct line to a mechanic you know personally when you have an emergency!). Finally and most importantly for us and companies like us we are able to grow our local business to provide a far greater service for our customers.

Don’t hesitate to contact us about any service request, regardless of vehicle age, brand or condition. We’ll be delighted to accommodate you as best we can.

Mercedes Star Diagnosis – fixing a modern car

Mercedes Star Diagnosis

Fixing modern vehicles involves a lot more than a decent toolbox these days. The key for any mechanic to get to the root cause of your car problems is always about having the right tool for the job and in the case of modern Mercedes-Benz cars, that tool is the Star Diagnosis diagnostic system. Linked directly to Mercedes in Germany via the internet, this tool always our mechanics access to the most essential systems in your vehicles onboard computer. Far from being a generic tool which can assist the investigating mechanic with a general idea of what the problem is, the Star system allows our mechanics gain precision information on your car and get to the cause of your problems accurately and efficiently avoiding the vagueness and uncertainty associated with many garages. With the assistance of this necessary tool our mechanics can not only cut down on their time spent researching your issues but use it to help explain the issues to our customers and allow them a far greater understanding of their own vehicles. A wonderfully accurate system which we are proud to say we run on a genuine contract from Mercedes-Benz which has helped us gain a reputation in Dublin as a reputable and experienced independent Mercedes garage.