The cursed trinity of diesel engines called AdBlue, EGR and DPF.
The fault light there again, shines like a full moon. Read about what it might be about in our information package.
To view our services for your car, we recommend starting from the home page .
For parts and equipment needs, click on our well-known hardware store -> Futurez.Fi .
If you haven’t been living under a rock, you’ve surely heard drivers complaining: the DPF filter is clogged, the EGR valve is stuck, or the AdBlue system is acting up.
These are systems designed to reduce emissions from modern engines. Unfortunately, they are also prone to failure and have a limited lifespan. To make matters worse, repairs often take a serious toll on your wallet.
However, the issue isn’t as black-and-white as the “gas pedal warriors” at the local coffee shop might claim. These systems are actually clever inventions—when they work properly and reliably. The trend a few years ago of removing or tampering with them just for fun or as a hobby was never a smart move, and no modern, responsible automotive business supports such
Quick jump to following sections -> EGR | DPF | ADBLUE
What these systems do, and most importantly why?
EGR puts your exhaust gasses for another round through the cylinders
Mission
EGR, or Exhaust Gas Recirculation, as the name suggests, redirects a portion of the engine’s exhaust gases back into the intake air. The amount of recirculated gas varies depending on conditions and load, and it is controlled by the EGR valve, which is managed by the ECU. These valves can operate either with an electronic servo or a vacuum actuator.
Why? EGR isn’t included in the engine bay just because manufacturers enjoy bolting on expensive components. The exhaust gas replaces some of the oxygen-rich intake air, reducing combustion temperatures in the cylinder. This, in turn, lowers nitrogen oxide (NOx) emissions by up to half.
When high-quality and appropriate oil is used, and the vehicle isn’t subjected solely to short 2-kilometer trips, the EGR and other systems can typically perform effectively for several hundred thousand kilometers. (Excluding models with obvious design flaws.)
Issues
As the image above illustrates, exhaust gas recirculation is a dirty job. The valve and its related pipes/channels become clogged over time. Eventually, or due to improper use, so much soot can accumulate that the valve gets stuck and stops functioning. This leads to engine misfires, warning lights, and ultimately the car entering limp mode, where engine power is limited.
Recommended solutions
The EGR valve can be cleaned proactively as part of regular maintenance to avoid issues. If problems have already occurred, simply driving the car won’t clean the valve, but physical cleaning can still help. If the situation has worsened significantly, the valve may need to be replaced. Additionally, the intake manifold can be cleaned or replaced, and the intake channels can, for instance, be grit-blasted to restore them to a clean state.
Illegal fixes to avoid
A common "quick fix" is EGR blanking, where exhaust gas recirculation is blocked by installing a metal plate in the channel and disabling the valve function in the ECU settings. Keep in mind that this is an illegal modification for vehicle inspections—and it does not address the soot buildup elsewhere in the intake system, which will continue to affect performance and fuel efficiency.
In summary: We recommend treating the EGR system as a regular maintenance item and taking preventive measures to avoid issues.
DPF collects your soot emissions, your car's very own vacuum cleaner dust bag.
Mission
You can think of the DPF filter and its cells as a vacuum cleaner bag. The soot particles produced by the engine are collected to prevent them from spreading into the surrounding environment, where they pose significant health risks to those who inhale them. The concept is great—until this "dust bag" becomes full.
Your engine has a trick up its sleeve for cleaning the DPF filter. When the fill level gets too high, a process called "regeneration" is triggered. The engine temporarily adjusts its settings to raise the exhaust gas temperature, burning off most of the soot from the filter at high heat.
For the DPF’s longevity, it’s crucial to use low-sulfur engine oil, which contributes less residue to the filter. It’s also important to regularly warm up the engine properly, for example, with longer highway drives. Short trips and poor-quality oil cause soot to accumulate faster than the system can clear it—and that’s when problems arise.
**Tip: Various vehicle issues can also be detrimental to the filter. For instance, a malfunction in the EGR system, glow plugs, mass airflow sensor, or other components can prevent the regeneration process from occurring—leading to yet another round of trouble.
Issues
As the filter fills up, the engine's performance and fuel efficiency begin to suffer. You might notice that your car is performing regeneration more and more frequently. Signs of a regeneration process include an elevated idle speed, a strange burnt smell, and a temporary increase in fuel consumption. Often, the engine's sound will change, the start/stop functions will deactivate, and the cooling fan might keep running even after you’ve parked the car.
Recommended solutions
Times do change, and these days, a DPF can be serviced with more than just a grinder and a scrap bin. Replacement parts are gradually becoming more available, and DPF cleaning solutions or a so-called forced regeneration can offer a temporary fix. A more effective remedy is a **DPF wash**, which has become reasonably priced thanks to new methods. As long as the filter is cleaned in time, a wash can often extend its lifespan by several years in one go.
Illegal fixes to avoid
Once upon a time, there was a period when DPF removal became a trend among car owners and industry professionals, as if it were some form of "prevention." This makes little sense. The procedure is illegal for inspections and can become costly if you’re forced to replace the filter entirely, which can run into thousands of euros. The increased exhaust smell isn’t exactly a welcome side effect either.
**In summary:** It's better to clean your DPF sooner rather than later. Use high-quality, low-sulfur engine oil and regularly warm up your engine properly. If you’re tuning your car, choose a programmer who avoids sloppy "rolling coal"-style smoky tunes that can damage the filter prematurely.
In Finland, DPF cleaning is offered by several trusted providers.
A functioning DPF filter is NOT a barrier to optimizing your car's performance, except in the case of extremely tuned hobby cars where exhaust flow capacity might genuinely become an issue.
Adblue - add some water in the tank, why on earth?
Mission
AdBlue has been in the headlines a lot, especially when its price briefly skyrocketed, leading people to stockpile urea in their bathrooms like toilet paper during the pandemic. It’s a system that became widespread around 2015, where a mixture of deionized water and urea is injected into your car’s catalytic converter. When heated, the liquid breaks down into ammonia and carbon dioxide. The ammonia then helps convert nitrogen oxides (NOx) into nitrogen and water, reducing emissions significantly—by up to two-thirds compared to before.
Detail of the day: this reaction is called selective catalytic reduction, which is where the abbreviation SCR, often seen in English, originates. As already mentioned in this article, this system is quite clever—at least until the warning light comes on.
Issues
SCR systems and their malfunctions sometimes cause panic, particularly because if the fluid runs out or the system fails, the car will eventually refuse to start altogether. This is electronically prevented.
The system includes components such as a tank, pump, level sensor, control unit, heater, and nozzle through which the mixture is dosed. Common issues include a faulty pump, a broken nozzle, or damage caused by freezing. When temperatures drop low enough, this fluid also freezes and begins to crystallize below -11°C. It’s easy to see why this is a bad idea in a closed system during a malfunction.
Recommended solutions
When it comes to the urea system, there’s not much the driver can do to influence its operation. Using high-quality fluid and regularly refilling the tank are practically the only preventive measures you can take. Repairs can be expensive if the system fails, as many manufacturers sell the components only as large assemblies rather than individual parts.
Illegal fixes to avoid
Especially the time the Amble fluid prices temporarily rose, disabling AdBlue systems became a hot topic in the automotive world. In such modifications, the AdBlue functions are shut off, and the monitoring systems are silenced, effectively making the car operate as if the system didn’t exist. However, before rushing into such solutions, remember that this procedure is also strictly illegal for vehicle inspections, and reactivating the system later is often not straightforward. Components left unused can deteriorate, and reactivation may require replacing parts entirely.
**In summary:** Use high-quality, season-appropriate AdBlue fluid, and keep up with your regular maintenance prayers. Think carefully before bypassing the system!
2023 Copyright © ECU Helsinki