AdBlue System Failures and Solutions: A Comprehensive Overview

AdBlue (SCR) System - NOx Emission Control in Modern Diesels
Increasing environmental awareness and stricter emission standards (Euro 4, 5, 6 and later) have led diesel engine manufacturers to develop innovative technologies to reduce harmful components in exhaust gases. One of these technologies is the Selective Catalytic Reduction (SCR) system, and the main additive used in this system is known as AdBlue. AdBlue is a special mixture of urea and deionized water and is used to convert harmful Nitrogen Oxide (NOx) emissions in the exhaust gases of diesel engines into harmless nitrogen gas (N2) and water vapor (H2O).
The AdBlue system has become a standard, especially in modern heavy vehicles (trucks, buses), construction machinery and many new generation diesel passenger cars. Although it is an environmentally sensitive technology, the AdBlue system may also encounter various failures over time. These failures can restrict the vehicle's performance, cause the engine fault lamp to light up, and even prevent the vehicle from starting in some cases.
In this comprehensive guide, we will discuss in detail how the AdBlue (SCR) system works, common causes of malfunctions, fault symptoms, diagnostic methods and professional solutions offered by Nitro Bilişim (AdBlue pump, injector, NOx sensor, heater failures and legal/environmental aspects of software solutions).
How Does the AdBlue (SCR) System Work?
The SCR system works by precisely spraying AdBlue liquid into the exhaust gas stream. AdBlue converts to ammonia (NH3) when it comes into contact with high-temperature exhaust gases. This ammonia reacts with NOx (Nitrogen Oxide and Nitrogen Dioxide) inside the SCR catalyst, decomposing them into harmless nitrogen gas and water vapor.
Basic Components of the AdBlue (SCR) System: * AdBlue Tank: It is a special tank where AdBlue liquid is stored.
* AdBlue Pump (Supply Module): It takes the AdBlue from the tank and sends it to the injector by pressurizing.
* AdBlue Injector (Dosage Module): It sprays a precise amount of AdBlue into the exhaust system according to the signals it receives from the ECU.
* SCR Catalyst: It is the main component in which NOx reacts with ammonia and turns into N2 and H2O.
* NOx Sensors: Located at the inlet and outlet of the SCR catalyst. It measures the NOx reduction efficiency of the system and provides feedback to the ECU.
* AdBlue Level and Quality Sensor: Measures the amount and sometimes the quality (density) of AdBlue in the warehouse.
* AdBlue Heater System: AdBlue liquid freezes at about -11°C. There are heating elements in the tank, pump and hoses to prevent freezing in cold climates.
* Control Unit (ECU/DCU): Manages the entire system, processes data from sensors and controls the pump and injector.
Common Causes of AdBlue System Failures
Since the AdBlue system consists of sensitive components, it can be affected by various factors: * AdBlue Pump Failure: The motor inside the pump burns out, cannot generate pressure, or leaks.
* AdBlue Injector Blockage or Malfunction: Blockage of the injector due to AdBlue crystallization or inability to spray properly.
• NOx Sensor Failure: Contamination, burning or incorrect measurement of the sensors. This can cause the system to misjudge its efficiency and generate a fault code.
* AdBlue Level or Quality Sensor Failure: Incorrect display of the quantity or quality of AdBlue in the warehouse.
* Malfunction of the AdBlue Heater Elements: Freezing of the AdBlue in cold weather and the system does not work.
* Contamination of AdBlue Liquid or Improper Liquid Use: Replacing AdBlue with water or another liquid, or contamination of AdBlue with substances such as fuel, oil, can cause serious damage to the system.
* AdBlue Crystallization: Crystallization may occur in the pipes and injector, especially if low-quality AdBlue is used or the system remains inactive for a long time.
* Wiring and Electrical Problems: Disconnection of cables leading to sensors, pumps or heaters, short circuit or corrosion of connectors.
* Software Problems: Software errors in the control unit.
Symptoms of AdBlue System Failure
* AdBlue Warning Light On: A warning light (usually yellow or red) for the AdBlue system lights up on the instrument panel.
* The Engine Fault Lamp (Check Engine) is Lit. * **