Concern: Engine light returning after AdBlue injector replacement
Fault Code: P20EEFD – “Efficiency of the SCR (Selective Catalytic Reduction) Bank 1 is Not Sufficient”
Customer Concern
The customer presented the vehicle after the AdBlue injector had been replaced with a genuine Mercedes-Benz part and the AdBlue tank had been topped up. The vehicle initially seemed fine, but the engine warning light later returned. Diagnostic checks revealed a stored fault code P20EEFD.
Initial Technical Assessment
Albert Nepomuceno, our Mercedes Master Technician, advised that AdBlue injectors are prone to crystallisation, which can restrict flow. In many cases, a thorough clean with warm/hot water resolves the issue; otherwise, replacement is required.
Since the injector had already been replaced, Albert noted that the injector adaptations must be reset during installation. This had not been done by the workshop.
Remote Support Intervention
We remotely connected to the workshop’s DrivePro 2 and performed the AdBlue injector adaptation reset live with the workshop technician.
Further Diagnostic Advice
As the injector may not have been the root cause, we advised the workshop to complete a NOx sensor functionality test using the DrivePro 2:
Conduct a 15-minute drive to bring the NOx sensors to operating temperature.
Perform a full-throttle acceleration for several seconds: both upstream and downstream NOx sensors should rise simultaneously up to approx. 1000 ppm.
On throttle lift-off/coasting, both sensors should drop close to 0 ppm (typically 20–30 ppm).
This test confirms whether the sensors are responding correctly and helps determine if the issue is with NOx sensing or AdBlue dosing into the catalyst.
Findings
During live data testing, the customer observed that both NOx sensors were reading incorrectly. Based on our diagnostic guidance, both sensors were replaced, adaptations were reset, Albert checked the software levels and identified available updates for the SCR and Engine Control Units. A full Remote Service was completed through the DrivePro 2 to update the modules and finish the repair.
Outcome
After completing the repairs and updates, the vehicle was road-tested. The P20EEFD fault did not return, and the AdBlue system is now operating correctly.
Result
Fault resolved. Vehicle operating as expected.
“Jeff Taylor from Sydney Eco Tune said that the level of support Opus IVS provides is invaluable for workshops, saving him and his team countless hours.”