AdBlue Service
AdBlue, SCR & NOx Sensor Diagnostics and Repairs
Book for AdBlue Service at Melbourne Euro now!AdBlue warning on? Engine light appearing? “No restart in XXX km” displayed on the dashboard? Modern diesel vehicles use sophisticated AdBlue and Selective Catalytic Reduction (SCR) systems to control nitrogen oxide emissions. When something goes wrong, the vehicle may display emissions warnings, reduce performance or eventually prevent an engine restart depending on the vehicle and fault.
Melbourne Euro provides specialist AdBlue diagnostics and repairs in Campbellfield, including NOx sensors, AdBlue pumps, injectors, tanks, heaters, pressure faults, SCR diagnosis and system calibration.
Rather than replacing components based on a fault code alone, we diagnose the complete system to determine why the fault has occurred.
Book your AdBlue diagnostic online or call Melbourne Euro on 1800 635 387.
What Is AdBlue?
AdBlue is a diesel exhaust fluid consisting of 32.5% high-purity urea and 67.5% demineralised water. It is stored in a separate tank and is not mixed with diesel fuel. During operation, a controlled quantity of AdBlue is injected into the exhaust system before the SCR catalyst. Under the correct exhaust conditions, it ultimately provides ammonia that allows the SCR catalyst to convert harmful nitrogen oxides into primarily nitrogen and water. The amount injected is carefully controlled by the vehicle’s engine and emissions-management systems.
What Is SCR?
SCR stands for Selective Catalytic Reduction. It is the exhaust after-treatment technology that uses AdBlue to reduce NOx emissions produced by diesel combustion. A modern SCR system can include:
- AdBlue tank
- AdBlue pump
- Pressure sensor
- Heated lines
- AdBlue dosing injector
- Temperature sensors
- SCR catalyst
- Upstream and downstream NOx sensors
- Electronic control systems
A fault with any of these components can potentially affect operation of the overall system.
What Is NOx?
NOx means nitrogen oxides, gases produced during high-temperature combustion. The SCR system is designed to significantly reduce the amount of NOx leaving the vehicle’s exhaust. Modern diesel vehicles commonly use NOx sensors before and/or after the SCR catalyst to monitor exhaust-gas conditions and determine whether the emissions system is operating correctly. This feedback is also why a failed NOx sensor can sometimes produce an AdBlue or SCR warning even when there is AdBlue in the tank.
How the AdBlue & SCR System Works
Typical diesel SCR system showing the AdBlue tank, pump, dosing injector, NOx sensors, SCR catalyst and exhaust-gas flow.
A simplified sequence is: Diesel Engine → Exhaust Gas → NOx Measurement → AdBlue Dosing → SCR Catalyst → NOx Reduction → Downstream Monitoring → Exhaust
The ECU continually monitors system operation and adjusts AdBlue dosing according to vehicle and exhaust conditions. If the expected NOx reduction isn’t achieved, the vehicle can store an SCR efficiency or dosing-system fault.
Watch: How AdBlue, SCR & NOx Sensors Work
Learn how AdBlue dosing, the SCR catalyst and NOx sensors work together in a modern diesel emissions system.
Common AdBlue Problems
An AdBlue warning doesn’t necessarily mean the vehicle simply needs more fluid.
Common faults can involve:
- Low AdBlue level
- Incorrect or contaminated AdBlue
- AdBlue crystallisation
- AdBlue pump failure
- Low system pressure
- AdBlue injector/dosing faults
- Blocked or restricted dosing injector
- AdBlue tank or level-sensor faults
- Tank or line heater faults
- NOx sensor failure
- Exhaust temperature sensor faults
- Wiring or communication faults
- SCR catalyst efficiency faults
- Software, adaptation or calibration issues
Correct diagnosis is important because several different faults can produce very similar dashboard warnings.
Melbourne Euro AdBlue & SCR Solutions
Full AdBlue System Diagnostics
We diagnose the system before replacing components. Depending on the vehicle and fault, testing may include Manufacturer-specific diagnostic scanning, Fault-code analysis, Live-data assessment, AdBlue pressure testing, Dosing-system testing, Pump operation, AdBlue injector activation, NOx sensor readings, Exhaust temperature data, Heater operation, Wiring and electrical testing, SCR efficiency assessment, This helps us distinguish between a failed component and a fault elsewhere in the emissions system.
AdBlue Pump, Tank & Heater Repairs
The AdBlue supply system must build and maintain the correct pressure for accurate dosing. We can diagnose and replace applicable: AdBlue pumps, Tank assemblies, Pressure sensors, Level sensors, Tank heaters, Delivery lines, Heating elements. Associated wiring and components, A P20E8 low-pressure fault, for example, doesn’t automatically mean the pump should be replaced. Pressure loss can have several possible causes that should be tested first.
AdBlue Injector & Dosing System
The dosing injector meters AdBlue into the exhaust. Deposits or crystallisation around the dosing system can interfere with correct operation, while electrical or mechanical injector faults can prevent correct dosing entirely. Melbourne Euro can inspect and test the dosing system and replace the injector where required.
NOx Sensor Diagnostics & Replacement
NOx sensors are critical to SCR system operation. A faulty sensor can provide incorrect feedback to the engine management system and trigger: Engine warning lights, SCR warnings, AdBlue faults, Emissions-system faults, Restart countdowns. We diagnose NOx sensor performance, electrical supply, wiring and communication faults before recommending replacement.
SCR Catalyst Diagnosis
Codes relating to SCR efficiency do not automatically prove the catalyst itself has failed. Before condemning an SCR catalyst, the wider system may need to be assessed for: Incorrect AdBlue dosing, AdBlue quality, NOx sensor accuracy, Exhaust temperature, Injector operation, System pressure, Other engine or emissions faults, This is particularly important with codes such as P20EE – SCR NOx catalyst efficiency below threshold.
Calibration, Reset & Adaptation
After certain AdBlue repairs, simply clearing the fault code may not complete the job. Depending on the manufacturer and repair, the vehicle may require applicable: System reset, Adaptation, Component initialisation, Learned-value reset, AdBlue level recognition, SCR functional testing, Manufacturer-specific procedures. Melbourne Euro uses specialist diagnostic equipment to perform applicable procedures after the repair.
Common AdBlue, SCR & NOx Fault Codes
| Fault Code | Common Description |
|---|---|
| P204F | Reductant / SCR system performance |
| P207F | AdBlue quality / reductant performance |
| P20E8 | AdBlue pressure too low |
| P20E9 | AdBlue pressure too high |
| P20EE | SCR NOx catalyst efficiency below threshold |
| P2047–P2049 | AdBlue dosing injector circuit faults |
| P2059 / P20BA | AdBlue heater faults |
| P2062–P2064 | AdBlue supply pump faults |
| P2065–P2069 | AdBlue level sensor faults |
| P2200 / P2201 | NOx sensor circuit / performance |
| P229F | NOx sensor 2 range / performance |
| U029D | Lost communication with NOx sensor |
The exact definition and diagnostic procedure can vary between manufacturers and engine-management systems. A fault code identifies where diagnosis should begin—it doesn’t necessarily identify the component that needs replacing.
Don’t Ignore an AdBlue Countdown
Some diesel vehicles use a distance countdown before engine restart is restricted when the SCR system detects certain unresolved faults or insufficient AdBlue.
If you’re seeing a message such as:
“No engine restart in 1,000 km”
“AdBlue system fault”
“Check AdBlue”
“Start not possible in XXX km”
don’t wait until the countdown reaches zero. The underlying fault should be diagnosed and repaired, followed by the applicable reset or confirmation procedure.
AdBlue, EGR & DPF – One Diesel Emissions System
AdBlue/SCR, EGR and the Diesel Particulate Filter (DPF) perform different jobs, but they operate as parts of the vehicle’s wider emissions-control strategy.
- EGR helps control NOx formation during combustion.
- DPF captures particulate matter and soot.
- AdBlue/SCR reduces NOx in the exhaust after combustion.
A problem elsewhere in the engine or emissions system can sometimes influence another system. That’s why Melbourne Euro looks beyond the dashboard warning and considers the complete diesel emissions system where appropriate.
Frequently Asked Questions
Why Is My AdBlue Light Still On After I Filled the Tank?
The warning may be caused by something other than low fluid. Possible causes include a pump, pressure, level sensor, NOx sensor, dosing injector, heater, SCR or electronic fault. Some vehicles may also require specific conditions or diagnostic procedures before the system recognises a repair.
Can a Faulty NOx Sensor Cause an AdBlue Warning?
Yes. NOx sensor information is used to monitor SCR operation, so an incorrect or failed sensor can contribute to SCR and AdBlue-related warnings.
What Does P20E8 Mean?
P20E8 generally indicates that reductant/AdBlue system pressure is too low. Possible causes can include the pump, pressure sensor, supply system, leakage, restriction or another dosing-system problem. The system should be tested before components are replaced.
What Does P20EE Mean?
P20EE generally relates to SCR NOx catalyst efficiency being below the expected threshold. This doesn’t automatically mean the SCR catalyst requires replacement. AdBlue dosing, NOx sensors, exhaust conditions and other system faults should also be considered.
How Much Does an AdBlue Repair Cost?
It depends on the fault and vehicle. A sensor or wiring problem is very different from an AdBlue tank, pump or SCR catalyst fault. Melbourne Euro diagnoses the system first and provides a quotation based on the repair actually required.
Can You Remove or Disable AdBlue?
For road vehicles, Melbourne Euro focuses on diagnosing and restoring the emissions system to correct operation, rather than disabling it.
Book an AdBlue Diagnostic in Melbourne
If your diesel vehicle has an AdBlue warning, SCR fault, NOx sensor code, emissions warning or restart countdown, have the system diagnosed before the problem progresses.
Melbourne Euro provides: AdBlue Diagnostics | SCR Diagnostics | NOx Sensors | AdBlue Pumps | Tanks & Heaters | Dosing Injectors | Pressure Faults | System Calibration
Book online or call 1800 635 387.
Melbourne Euro – European Vehicle Specialists
4/23 Cooper Street, Campbellfield VIC 3061