Mercedes AdBlue Fault Codes: Diagnosis, Solutions, and Prevention

Mercedes Adblue Fault Codes can be a frustrating issue for vehicle owners. At CARDIAGTECH.NET, we provide comprehensive solutions for diagnosing, resolving, and preventing these problems, ensuring your Mercedes runs smoothly. We offer high-quality diagnostic tools to swiftly identify and address these faults, restoring your vehicle’s optimal performance.

1. Understanding Mercedes AdBlue Systems and Fault Codes

1.1 What is AdBlue and How Does It Work in Mercedes Vehicles?

AdBlue, also known as Diesel Exhaust Fluid (DEF), is a non-toxic solution of urea and deionized water used in Mercedes diesel vehicles equipped with Selective Catalytic Reduction (SCR) systems. The SCR system reduces harmful nitrogen oxides (NOx) emissions by injecting AdBlue into the exhaust stream. According to a study by the European Automobile Manufacturers Association (ACEA), SCR systems can reduce NOx emissions by up to 90%.

The AdBlue injection process occurs as follows:

Storage: AdBlue is stored in a dedicated tank in the vehicle.
Injection: When the engine is running, the vehicle’s electronic control unit (ECU) calculates the required amount of AdBlue based on factors like exhaust temperature, engine load, and NOx levels. A pump delivers AdBlue from the tank to an injector located in the exhaust system, upstream of the SCR catalyst.
Catalytic Conversion: Once injected, the AdBlue decomposes into ammonia (NH3) and carbon dioxide (CO2). The ammonia then reacts with the NOx in the SCR catalyst, converting them into harmless nitrogen (N2) and water (H2O).

Alt Text: AdBlue tank location in a Mercedes-Benz vehicle, showing the blue filler cap.

1.2 Why Do Mercedes AdBlue Fault Codes Occur?

Mercedes AdBlue fault codes can arise from various issues within the SCR system. Common causes include:

Contaminated or Expired AdBlue: According to a report by the Vehicle Certification Agency (VCA), using low-quality or expired AdBlue can lead to system malfunctions and fault codes.
Faulty Sensors: NOx sensors, DEF level sensors, and temperature sensors can fail, providing incorrect data to the ECU.
Clogged Injectors or Filters: The AdBlue injector and filter can become clogged with crystallized urea, restricting flow.
Pump Failures: The AdBlue pump may fail to deliver the required amount of fluid.
Heater Malfunctions: In cold weather, the AdBlue system relies on heaters to prevent freezing. If these heaters fail, the system may not function correctly.
Software Issues: Glitches or outdated software in the ECU can trigger false fault codes.
Wiring and Connection Problems: Damaged or corroded wiring and connectors can disrupt the system’s electrical signals.
Exhaust Leaks: Leaks in the exhaust system can affect the SCR catalyst’s efficiency, leading to fault codes.

1.3 What are the Symptoms of Mercedes AdBlue System Issues?

Several symptoms can indicate problems with the Mercedes AdBlue system:

Warning Lights: The most common symptom is the illumination of the AdBlue warning light on the dashboard.
Error Messages: The vehicle’s display screen may show messages like “AdBlue System Malfunction,” “Check AdBlue Level,” or “Engine Start Not Possible.”
Reduced Engine Power: The ECU may limit engine power to reduce emissions if it detects an AdBlue system fault.
Engine Start Prevention: In some cases, the vehicle may prevent engine start if the AdBlue system is severely compromised.
Increased Emissions: A malfunctioning AdBlue system can lead to higher NOx emissions, which may be detected during vehicle inspections.

2. Common Mercedes AdBlue Fault Codes and Their Meanings

Here’s a breakdown of common Mercedes AdBlue fault codes, their potential causes, and possible solutions. CARDIAGTECH.NET provides the diagnostic tools you need to accurately identify these issues.

Fault Code	Description	Possible Causes	Solutions
P20E8	Reductant Pressure Too Low	DEF pump failure, clogged DEF filter, low DEF level	Check DEF level, replace DEF filter, test DEF pump, inspect for leaks
P20E9	Reductant Pressure Too High	Blocked DEF injector, faulty DEF pressure sensor	Clean or replace DEF injector, test DEF pressure sensor
P20EE	SCR NOx Catalyst Efficiency Below Threshold	SCR catalyst failure, poor quality DEF, NOx sensor fault	Test SCR catalyst, use high-quality DEF, test NOx sensors
P204F	Reductant System Performance	DEF quality issues, DEF injection system problems, SCR catalyst issues	Check DEF quality, inspect DEF injection system, test SCR catalyst
P207F	Reductant Quality Performance	Contaminated DEF, improper DEF concentration, sensor issues	Replace DEF, check DEF concentration, test DEF quality sensor
P203B	Reductant Level Sensor Circuit Range/Performance	Faulty DEF level sensor, wiring issues, low DEF level	Check DEF level, test DEF level sensor, inspect wiring
P203C	Reductant Level Sensor Circuit Low	DEF level sensor failure, wiring problems, low DEF level	Check DEF level, test DEF level sensor, inspect wiring
P203D	Reductant Level Sensor Circuit High	DEF level sensor issues, wiring or connector problems	Test DEF level sensor, inspect wiring and connectors
P2047	Reductant Injection Air Pressure Sensor Circuit	Faulty air pressure sensor, wiring issues, air supply problems	Test air pressure sensor, inspect wiring, check air supply
P2048	Reductant Injection Air Pressure Sensor Circuit Low	Sensor failure, wiring issues, air supply problems	Test air pressure sensor, inspect wiring, check air supply
P2049	Reductant Injection Air Pressure Sensor Circuit High	Sensor failure, wiring issues, air supply problems	Test air pressure sensor, inspect wiring, check air supply
P205B	Reductant Tank Temperature Sensor Circuit Range/Performance	Faulty temperature sensor, wiring issues, sensor malfunction	Test temperature sensor, inspect wiring
P205C	Reductant Tank Temperature Sensor Circuit Low	Temperature sensor issues, wiring or connector problems	Test temperature sensor, inspect wiring and connectors
P205D	Reductant Tank Temperature Sensor Circuit High	Sensor issues, wiring or connector problems	Test temperature sensor, inspect wiring and connectors
P206A	Reductant Quality Sensor Circuit	Faulty DEF quality sensor, wiring issues, contaminated DEF	Test DEF quality sensor, inspect wiring, replace DEF
P206B	Reductant Quality Sensor Circuit Range/Performance	DEF quality sensor failure, wiring or connector problems	Test DEF quality sensor, inspect wiring and connectors
P206C	Reductant Quality Sensor Circuit Low	DEF quality sensor issues, wiring or connector problems	Test DEF quality sensor, inspect wiring and connectors
P206D	Reductant Quality Sensor Circuit High	DEF quality sensor issues, wiring or connector problems	Test DEF quality sensor, inspect wiring and connectors
P13DF	AdBlue Reductant Metering Unit Malfunction	Faulty reductant metering unit, wiring issues, connector problems	Test reductant metering unit, inspect wiring and connectors
P13E0	AdBlue System Malfunction – Pressure Line Heater 1	Faulty pressure line heater, wiring issues, heater malfunction	Test pressure line heater, inspect wiring
P13E1	AdBlue System Malfunction – Pressure Line Heater 2	Faulty pressure line heater, wiring issues, heater malfunction	Test pressure line heater, inspect wiring
P13E2	AdBlue System Malfunction – Return Line Heater	Faulty return line heater, wiring issues, heater malfunction	Test return line heater, inspect wiring
P13E3	AdBlue System Malfunction – Heater Circuit	Faulty heater circuit, wiring issues, connector problems	Test heater circuit, inspect wiring and connectors
P13E4	AdBlue System Malfunction – Reductant Pump	Faulty reductant pump, wiring issues, connector problems	Test reductant pump, inspect wiring and connectors
P13E5	AdBlue System Malfunction – Reductant Injector	Faulty reductant injector, wiring issues, injector malfunction	Test reductant injector, inspect wiring
P13E6	AdBlue System Malfunction – Temperature Sensor	Faulty temperature sensor, wiring issues, sensor malfunction	Test temperature sensor, inspect wiring

Alt Text: A close-up of a Mercedes-Benz AdBlue injector, crucial for the SCR system.

3. Step-by-Step Guide to Diagnosing Mercedes AdBlue Faults

Here is a detailed, step-by-step guide to diagnosing Mercedes AdBlue faults. Remember, CARDIAGTECH.NET offers the tools and resources you need for each of these steps.

3.1 Step 1: Retrieve the Fault Code

Use an OBD-II scanner to retrieve the specific fault code from the vehicle’s ECU. Note down the code and its description. According to research from the National Institute for Automotive Service Excellence (ASE), accurate fault code retrieval is the first critical step in diagnosing any automotive issue.

3.2 Step 2: Check the AdBlue Level and Quality

Verify the AdBlue tank’s fluid level. If low, refill with high-quality AdBlue that meets ISO 22241 standards. Inspect the fluid for contamination or unusual color. Use a refractometer to check the AdBlue concentration, which should be around 32.5%.

3.3 Step 3: Inspect the AdBlue System Components

Visually inspect the AdBlue tank, pump, injector, and lines for leaks, damage, or corrosion. Check the electrical connectors for proper seating and signs of corrosion.

3.4 Step 4: Test the AdBlue Pump

Use a multimeter to check the voltage and current supply to the AdBlue pump. If there is no power, check the fuses and relays. If power is present but the pump is not running, the pump may be faulty and need replacement.

3.5 Step 5: Test the AdBlue Injector

Remove the AdBlue injector and inspect it for clogs or deposits. Use an ultrasonic cleaner to clean the injector nozzle. Test the injector’s spray pattern and volume using a suitable test bench. Replace the injector if it is faulty.

3.6 Step 6: Test the Sensors

Use a scan tool to monitor the readings from the NOx sensors, DEF level sensor, and temperature sensors. Compare the readings with the manufacturer’s specifications. Replace any sensors that are providing incorrect data. A study by Bosch indicates that faulty sensors are a leading cause of AdBlue system problems.

3.7 Step 7: Check the Wiring and Connections

Use a multimeter to check the continuity and resistance of the wiring between the sensors, pump, injector, and ECU. Repair any damaged or corroded wires and connectors.

3.8 Step 8: Perform a System Test

Use a diagnostic scan tool to perform a system test of the AdBlue system. This test can activate the pump and injector, and monitor the sensor readings. Follow the manufacturer’s instructions for performing the system test.

Alt Text: A diagnostic scan tool being used to check Mercedes-Benz AdBlue system parameters.

4. Solutions for Common Mercedes AdBlue Fault Codes

Based on the diagnosis, here are solutions for common Mercedes AdBlue fault codes. CARDIAGTECH.NET provides all the necessary components and tools to carry out these repairs.

4.1 Replacing a Faulty AdBlue Pump

Disconnect the Battery: Disconnect the negative terminal of the battery to prevent electrical damage.
Access the Pump: Locate the AdBlue pump, typically near the AdBlue tank. Remove any covers or shields to access the pump.
Disconnect the Lines and Electrical Connector: Disconnect the AdBlue lines from the pump, taking care to avoid spills. Disconnect the electrical connector.
Remove the Old Pump: Unbolt the old pump from its mounting bracket and remove it.
Install the New Pump: Install the new pump in the mounting bracket and bolt it in place.
Connect the Lines and Electrical Connector: Connect the AdBlue lines to the new pump, ensuring they are securely attached. Connect the electrical connector.
Reconnect the Battery: Reconnect the negative terminal of the battery.
Perform a System Test: Use a diagnostic scan tool to perform a system test of the AdBlue system and verify that the new pump is functioning correctly.

4.2 Cleaning or Replacing a Clogged AdBlue Injector

Disconnect the Battery: Disconnect the negative terminal of the battery.
Access the Injector: Locate the AdBlue injector in the exhaust system.
Disconnect the Electrical Connector: Disconnect the electrical connector from the injector.
Remove the Injector: Carefully unscrew the injector from the exhaust system.
Clean the Injector (if applicable): If the injector is not severely clogged, you can try cleaning it using an ultrasonic cleaner or a specialized injector cleaning solution.
Install the New or Cleaned Injector: Install the new or cleaned injector into the exhaust system and tighten it to the specified torque.
Connect the Electrical Connector: Connect the electrical connector to the injector.
Reconnect the Battery: Reconnect the negative terminal of the battery.
Perform a System Test: Use a diagnostic scan tool to perform a system test of the AdBlue system and verify that the injector is functioning correctly.

4.3 Replacing a Faulty NOx Sensor

Disconnect the Battery: Disconnect the negative terminal of the battery.
Access the Sensor: Locate the NOx sensor in the exhaust system. There may be one or two sensors, depending on the vehicle model.
Disconnect the Electrical Connector: Disconnect the electrical connector from the sensor.
Remove the Old Sensor: Carefully unscrew the old sensor from the exhaust system.
Install the New Sensor: Install the new sensor into the exhaust system and tighten it to the specified torque.
Connect the Electrical Connector: Connect the electrical connector to the sensor.
Reconnect the Battery: Reconnect the negative terminal of the battery.
Calibrate the Sensor (if necessary): Some NOx sensors may require calibration using a diagnostic scan tool. Follow the manufacturer’s instructions for calibration.
Perform a System Test: Use a diagnostic scan tool to perform a system test of the AdBlue system and verify that the sensor is functioning correctly.

4.4 Clearing Fault Codes

After performing any repairs or replacements, use a diagnostic scan tool to clear the fault codes from the vehicle’s ECU. Drive the vehicle for a short distance to ensure that the fault codes do not reappear.

5. Preventing Mercedes AdBlue Faults

Prevention is always better than cure. Here are some tips to help prevent Mercedes AdBlue faults. CARDIAGTECH.NET can provide the products and advice to keep your system running smoothly.

Use High-Quality AdBlue: Always use AdBlue that meets ISO 22241 standards. Avoid using expired or contaminated AdBlue.
Regularly Check the AdBlue Level: Keep the AdBlue tank filled to the recommended level.
Proper Storage of AdBlue: Store AdBlue in a cool, dry place, away from direct sunlight.
Avoid Contamination: Use a clean funnel when filling the AdBlue tank to prevent contamination.
Regular System Checks: Periodically check the AdBlue system components for leaks, damage, or corrosion.
Software Updates: Keep the vehicle’s ECU software up to date to ensure proper AdBlue system operation. According to a study by the American Automobile Association (AAA), regular maintenance and software updates can significantly reduce the risk of vehicle malfunctions.

6. The Role of Diagnostic Tools in Addressing AdBlue Faults

Diagnostic tools are essential for accurately identifying and resolving Mercedes AdBlue faults. These tools allow technicians to:

Retrieve Fault Codes: Quickly retrieve and interpret fault codes from the vehicle’s ECU.
Monitor Sensor Readings: Monitor the real-time data from the various sensors in the AdBlue system.
Perform System Tests: Activate the AdBlue pump and injector, and monitor the system’s response.
Calibrate Sensors: Calibrate new or replacement sensors.
Clear Fault Codes: Clear fault codes from the vehicle’s ECU after repairs have been made.

CARDIAGTECH.NET offers a range of high-quality diagnostic tools that are specifically designed for diagnosing and repairing Mercedes AdBlue systems. Our tools are user-friendly and provide accurate and reliable results.

7. Why Choose CARDIAGTECH.NET for Your AdBlue Needs?

At CARDIAGTECH.NET, we are committed to providing our customers with the best possible products and services for their Mercedes AdBlue system needs. Here’s why you should choose us:

Expertise: We have extensive knowledge and experience in diagnosing and repairing Mercedes AdBlue systems.
Quality Products: We offer a wide range of high-quality diagnostic tools, replacement parts, and AdBlue fluid that meet or exceed OEM standards.
Competitive Prices: We offer competitive prices on all of our products and services.
Excellent Customer Service: We are dedicated to providing our customers with excellent customer service and support.
Comprehensive Solutions: We offer comprehensive solutions for diagnosing, resolving, and preventing Mercedes AdBlue faults.

Alt Text: A selection of CARDIAGTECH diagnostic tools designed for Mercedes-Benz vehicles.

8. Case Studies: Resolving Mercedes AdBlue Issues with CARDIAGTECH.NET Tools

Here are a few case studies demonstrating how CARDIAGTECH.NET tools can effectively resolve Mercedes AdBlue issues.

8.1 Case Study 1: P20E8 – Reductant Pressure Too Low

Vehicle: 2017 Mercedes-Benz E350 BlueTEC

Fault Code: P20E8 – Reductant Pressure Too Low

Symptoms: AdBlue warning light, reduced engine power

Diagnosis: Using a CARDIAGTECH.NET diagnostic tool, the technician retrieved the P20E8 fault code. Further testing revealed that the AdBlue pump was not delivering sufficient pressure.

Solution: The technician replaced the faulty AdBlue pump with a new pump from CARDIAGTECH.NET. After replacing the pump, the technician performed a system test using the diagnostic tool and cleared the fault codes. The vehicle was then test-driven, and the AdBlue system functioned correctly.

8.2 Case Study 2: P20EE – SCR NOx Catalyst Efficiency Below Threshold

Vehicle: 2015 Mercedes-Benz ML250 BlueTEC

Fault Code: P20EE – SCR NOx Catalyst Efficiency Below Threshold

Symptoms: AdBlue warning light, increased emissions

Diagnosis: Using a CARDIAGTECH.NET diagnostic tool, the technician retrieved the P20EE fault code. The NOx sensor readings were also abnormal.

Solution: The technician replaced the faulty NOx sensor with a new sensor from CARDIAGTECH.NET. After replacing the sensor, the technician calibrated the sensor using the diagnostic tool and cleared the fault codes. The vehicle was then test-driven, and the AdBlue system functioned correctly with normal NOx emissions.

8.3 Case Study 3: P207F – Reductant Quality Performance

Vehicle: 2019 Mercedes-Benz C300d

Fault Code: P207F – Reductant Quality Performance

Symptoms: AdBlue warning light, “Check AdBlue Quality” message

Diagnosis: Using a CARDIAGTECH.NET diagnostic tool, the technician retrieved the P207F fault code. A refractometer test of the AdBlue fluid revealed that the concentration was outside the acceptable range.

Solution: The technician drained the contaminated AdBlue fluid and refilled the tank with high-quality AdBlue from CARDIAGTECH.NET. After refilling the tank, the technician cleared the fault codes and performed a system test. The vehicle was then test-driven, and the AdBlue system functioned correctly.

9. Mercedes AdBlue System: FAQs

9.1 What happens if I ignore the AdBlue warning light?

Ignoring the AdBlue warning light can lead to reduced engine power, engine start prevention, and increased emissions. It can also cause damage to the SCR catalyst, which can be expensive to replace.

9.2 Can I use any brand of AdBlue in my Mercedes?

No, you should only use AdBlue that meets ISO 22241 standards. Using low-quality or contaminated AdBlue can damage the AdBlue system.

9.3 How often do I need to refill the AdBlue tank?

The frequency of AdBlue refills depends on the vehicle model, driving conditions, and engine load. On average, you may need to refill the AdBlue tank every 5,000 to 10,000 miles.

9.4 Can I reset the AdBlue warning light myself?

In some cases, you may be able to reset the AdBlue warning light by refilling the AdBlue tank. However, if there is an underlying issue with the AdBlue system, the warning light will reappear. It is best to diagnose and resolve the underlying issue before resetting the warning light.

9.5 Is it safe to drive with an AdBlue system fault?

It may be safe to drive for a short distance with an AdBlue system fault, but it is not recommended. The vehicle may have reduced engine power, and you may be contributing to higher emissions. It is best to have the AdBlue system repaired as soon as possible.

9.6 How do I know if my AdBlue is contaminated?

Contaminated AdBlue may have a cloudy or discolored appearance. It may also have a strange odor. If you suspect that your AdBlue is contaminated, it is best to drain the tank and refill it with fresh AdBlue.

9.7 Can cold weather affect the AdBlue system?

Yes, cold weather can cause the AdBlue fluid to freeze. Mercedes vehicles are equipped with heaters to prevent freezing. However, if the heaters malfunction, the AdBlue system may not function correctly in cold weather.

9.8 What is the lifespan of an AdBlue injector?

The lifespan of an AdBlue injector can vary depending on the quality of the AdBlue used and the operating conditions. On average, an AdBlue injector may last for 50,000 to 100,000 miles.

9.9 How much does it cost to repair an AdBlue system fault?

The cost to repair an AdBlue system fault can vary depending on the nature of the problem and the parts required. A simple repair, such as replacing a faulty sensor, may cost a few hundred dollars. A more complex repair, such as replacing the SCR catalyst, may cost several thousand dollars.

9.10 Where can I find a qualified technician to repair my Mercedes AdBlue system?

You can find a qualified technician to repair your Mercedes AdBlue system by searching online for Mercedes-Benz specialists in your area. You can also ask for recommendations from friends, family, or other Mercedes-Benz owners.

10. Contact CARDIAGTECH.NET for Expert Assistance

If you’re experiencing Mercedes AdBlue fault codes or need assistance with your AdBlue system, don’t hesitate to contact us at CARDIAGTECH.NET. Our team of experts is ready to help you diagnose and resolve your AdBlue issues quickly and efficiently. We offer a wide range of diagnostic tools, replacement parts, and expert advice to keep your Mercedes running smoothly.

Contact Information:

Address: 276 Reock St, City of Orange, NJ 07050, United States
WhatsApp: +1 (641) 206-8880
Website: CARDIAGTECH.NET

Let CARDIAGTECH.NET be your trusted partner for all your Mercedes AdBlue needs. Contact us today and experience the difference!

By providing high-quality diagnostic tools and expert support, CARDIAGTECH.NET ensures that Mercedes owners can effectively address AdBlue fault codes, maintaining optimal vehicle performance and reducing emissions. Contact us today to learn more about our products and services, and let us help you keep your Mercedes running smoothly.