To repair the car from the EGR error that appeared for second time I booked an appointment with Dallas Motorsport in Thessaloniki. Yesterday, finally I received a phone call from them to pick up the car.
Having spent days in thoroughly investigating the reoccurring EGR error, their diagnosis showed the following:
Mass Airflow Sensor (MAF)
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Technically speaking, the MAF monitors the EGR and if the airflow is lower from what the ECU expects, it will think there is an EGR problem. Despite the fact that no error appeared while scanning with ODIS, as a first step, a used MAF in working condition replaced my old one. The P040100 EGR fault went away immediately and did not reappear even after 600 km of test driving. To be fully safe, the used MAF was removed and a brand new MAF (04L906461B) was installed. But there was still black smoke coming out of the exhaust…
Diesel Particulate Filter (DPF)
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As we all know, a functional DPF should not let any soot out of the exhaust. Even in the case of incomplete combustion the DPF should keep all soot but regenerate sooner than usual. In my case soot was present but there was no error related to the DPF in ODIS. Additionally, regenerations took in 320-645 km intervals which is considered normal. So, my DPF was sent to a specialist for evaluation (I remind you that this DPF replaced the factory installed one some months ago to fight the first appearance of P040100 error some months ago). The specialist concluded that the DPF installed was not effective in capturing soot. The DPF being faulty, the decision was that it should be replaced. The DPF to be replaced was installed by the same technician few months ago. As a good will gesture, the new DPF was installed free of charge. Very honest customer approach.
Further investigation
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With the new MAF and DPF the problems appear to be solved. To be on the safe side, before reassembling the engine parts, some further investigation took place:
* The turbine was dismantled and send to a turbine specialist. His verdict was that my turbine is still good after 120000 km despite continuously using Start-Stop (it is said that turbine suffers from the numerous vicious cycles of spinning and stopping). That saved me hundreds of euros (a new Garrett turbine 847671-5004S costs 855€ and a VW 04L253020S turbine costs approximately 1850€)
* The intake manifold was removed and examined. It was really filthy from soot and therefore was cleaned.
* The EGR was cleaned from soot coming from the faulty DPF.
Final result
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The final result of all interventions was an error free car. Now there is no peculiar smell in the cabin too… The engine is running smoothly and the whole driving experience is restored. Of course, in the following days I will be testing the behaviour of te car and I will update the current post.
To anyone facing the EGR P040100 error, I hope my experience helps you.
After replacing EGR, DPF, MAF, injectors, differential pressure sensor and cleaning the intake manifold, I wish I don't face any time soon another DPF or EGR issue. For sure I am very sceptical about pars failing without producing errors in ODIS diagnosis.
Until the next problem, I wish all of you, enjoyable rides!