Adblue System Malfunctions (Here Is How To Solve)

adblue system malfunction

‍Have you ever wondered how to fix Adblue system system malfunction? Well, we got you covered.

An AdBlue system malfunction can be a common issue faced by many vehicle owners, especially those driving diesel-powered models.

AdBlue, also known as Diesel Exhaust Fluid (DEF), is a solution of urea in water that plays a crucial role in reducing harmful nitrogen oxide (NOx) emissions from diesel vehicles.

It does this by injecting the solution into the exhaust gases as part of the Selective Catalytic Reduction (SCR) process.

This process converts up to 90% of a vehicle’s harmful NOx emissions into nitrogen and water. Modern diesel-powered vehicles combine AdBlue with other emission control systems to meet the highest emission standards while retaining high engine power outputs and fuel economy.

However, like any other automotive system, the AdBlue system can experience malfunctions, which can lead to reduced performance and potential damage if not addressed promptly.

We will cover the causes of the malfunction, the warning signs to look out for, and the steps to take when resetting the system. So, let’s dive in and explore this topic in depth.

How Does the AdBlue System Work?

Components and Function

The AdBlue system consists of several components, including an external storage tank with an internal delivery pump, an injection valve, a heater element, and an Electronic Diesel Control (EDC) unit.

The AdBlue solution is stored in the external tank, from which it is injected into the exhaust gas stream through the injection valve.

To prevent the AdBlue solution from freezing in low outside temperatures, a heater element is installed in the tank.

The EDC unit controls the activation and dosing of AdBlue based on several parameters, such as exhaust temperature, NOx content before and after the SCR catalytic converter, and the operational readiness of the AdBlue system itself.

The AdBlue system in your vehicle will only start working when all these parameters are fulfilled.

Importance of AdBlue

The primary purpose of the AdBlue system is to reduce NOx emissions from diesel vehicles, which contribute to air pollution and pose health risks.

By converting harmful NOx emissions into nitrogen and water, the AdBlue system helps diesel vehicles meet stringent emission standards and reduce their environmental impact.

Additionally, the AdBlue system also ensures that diesel vehicles maintain high engine power outputs and fuel economy, making it an essential component for modern diesel vehicle owners.

Fixing AdBlue System Malfunction

Depending on the cause of the AdBlue system malfunction, you may need to take the following corrective actions:

Replace the In-Tank Heater Element

If the heater element in the AdBlue tank has burned out, you will need to replace it with a new one.

Consult your vehicle manufacturer’s guidelines for the appropriate replacement part and installation procedures.

Clean or Replace the Injector and Connecting Tubing

If the injector and connecting tubing are clogged, you may need to clean or replace these components.

Consult your vehicle manufacturer’s guidelines for the appropriate cleaning and replacement procedures.

Service or Replace the NOx Sensor

If the NOx sensor is faulty, you may need to service or replace it. Consult your vehicle manufacturer’s guidelines for the appropriate servicing and replacement procedures.

Common Causes of AdBlue System Malfunction

Although the AdBlue system is relatively simple, it is sensitive and delicate. Some of the common causes of AdBlue system malfunction include:

In-Tank Heater Element Failure

The heater element in the AdBlue tank can burn out, requiring replacement with a new one. This component is essential for preventing the AdBlue solution from freezing in low outside temperatures, so its failure can lead to system malfunctions and reduced performance.

Injector and Connecting Tubing Clogging

The AdBlue injector and connecting tubing can become clogged if the system operates only at high exhaust temperatures and the vehicle is used for frequent short journeys.

This can cause the urea solution to crystallize and obstruct the flow of AdBlue, leading to system malfunctions and reduced emission control effectiveness.

NOx Sensor Issues

The NOx sensor, which monitors the NOx content before and after the SCR catalytic converter, can break or provide false readings.

This can result in incorrect AdBlue dosing and system malfunctions, as well as increased emissions and potential damage to the catalytic converter.

AdBlue System Malfunction Warning Signs

When there is a problem with the AdBlue system, your vehicle will display warning messages and illuminate warning lights on the dashboard. Depending on the model, you may encounter some of the following messages:

  • AdBlue Check Additive See Operator’s Manual
  • AdBlue Range
  • Engine Start Not Permitted (AdBlue Empty)
  • Check AdBlue. No engine Start is Possible in XXX miles/km.
  • Check AdBlue Remaining starts X.

These warning messages indicate that there may be an issue with the AdBlue system, such as low DEF fluid levels or a fault with the SCR system. It is crucial to address these issues promptly to prevent further damage and maintain your vehicle’s emission control effectiveness.

Preparing to Reset the AdBlue System Malfunction

Before attempting to reset the AdBlue system malfunction, it is essential to ensure that all potential issues have been addressed. Here are some steps to take before resetting the system:

  1. Check AdBlue Levels: Ensure that your AdBlue tank is adequately filled. If the tank is low, top it up with a high-quality AdBlue solution.
  2. Inspect for Leaks: Check for any visible leaks in the AdBlue system, including the tank, hoses, and injector. If you find any leaks, have them repaired before attempting to reset the system.
  3. Clean AdBlue Injector: If you suspect that your AdBlue injector may be blocked or dirty, clean it to ensure optimal performance. This can usually be done with a specialized cleaning solution designed for AdBlue injectors.
  4. Replace Faulty Sensor: If you believe that the AdBlue sensor is faulty, replace it with a new one. This will ensure that the ECU receives accurate information about the AdBlue system’s status.
  5. Check SCR System: Inspect the SCR system for any signs of damage or malfunction. If you find any issues, have them repaired before attempting to reset the AdBlue system.

Resetting the AdBlue System Malfunction

Once you have addressed any potential issues within the AdBlue system, it is time to reset the malfunction.

There are several methods for doing this, and the specific process may vary depending on your vehicle’s make and model.

Here are some common methods for resetting the AdBlue system malfunction:

  1. Self-Reset: In some cases, the AdBlue system malfunction may automatically reset itself once the issue has been resolved. This could involve topping up the AdBlue tank or replacing a faulty sensor. Once the problem is fixed, the warning message may disappear from your dashboard after driving for a short period.
  • Ignition Reset: Another method for resetting the AdBlue system malfunction involves turning the vehicle’s ignition to the ‘Run’ position without starting the engine. Hold the ignition in this position for 20-60 seconds, then turn it off and start the engine. This process may help to reset the system and clear the warning message.
  • Battery Disconnect: Disconnecting the vehicle’s battery for a short period can also help to reset the AdBlue system malfunction. Ensure that the engine is off, and then disconnect the battery for 10-15 minutes. Reconnect the battery and start the engine to see if the warning message has been cleared.
  • Diagnostic Tool Reset: If the above methods do not work, you may need to use a diagnostic tool to reset the AdBlue system malfunction. A professional-grade diagnostic tool can communicate with your vehicle’s ECU and clear any error codes related to the AdBlue system. This process should be performed by a qualified technician, as it requires specialized equipment and knowledge.

Preventing AdBlue System Malfunction

To minimize the risk of AdBlue system malfunction, follow these best practices:

Regularly Check AdBlue Levels

Regularly check the AdBlue level in your vehicle and top it up as needed. You can purchase AdBlue fluid from a Mercedes dealer or a generic Diesel Exhaust Fluid from auto part stores or gas stations.

Ensure that you add AdBlue to the correct tank and do not mix it with diesel fluid, as AdBlue is neither an additive nor a lubricant. Additionally, avoid mixing water with AdBlue.

Perform Scheduled Maintenance

Adhere to your vehicle manufacturer’s recommended maintenance schedule for the AdBlue system, including cleaning or replacing the injector and connecting tubing, replacing the in-tank heater element, and servicing the NOx sensor.

Regular maintenance can help prevent system malfunctions and ensure optimal emission control performance.

Avoid Short Journeys

Frequent short journeys can cause the urea solution in the AdBlue system to crystallize, leading to the injector and connecting tubing clogging.

Try to minimize short journeys and allow your vehicle to reach optimal operating temperatures to avoid this issue.

Diagnosing AdBlue System Malfunction

If you suspect that your AdBlue system is malfunctioning, perform the following checks:

  • Verify the AdBlue level and top it up if needed.
  • Inspect the values from the temperature sensor upstream of the SCR catalytic converter.
  • Check the values from the NOx sensor control unit upstream and downstream of the SCR catalytic converter.
  • Assess the AdBlue tank for DEF quality and quantity.
  • Examine the AdBlue delivery pump and injection valve for proper operation.
  • Evaluate the AdBlue metering amount.
  • Visually check for leaks in the system.

If you are unable to diagnose the issue yourself, consult a certified technician who can help you refill your tank or diagnose and fix any problems you may be experiencing with your AdBlue system.

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In conclusion, understanding the common causes and warning signs of AdBlue system malfunction, as well as how to prevent, diagnose, and fix these issues, can help you maintain your diesel vehicle’s emission control effectiveness and overall performance.

Always consult your vehicle manufacturer’s guidelines and consult a certified technician if you are unsure about any aspect of your AdBlue system maintenance.

Stephan K.

I have been working as a mechanic for over 13 years and have been deeper into advanced automotive diagnostics for some years.

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