Customer concern
An AdBlue fault with a no-start countdown
This 2019 Vauxhall Grandland X was presented to MPH Northwest with an AdBlue/SCR system fault requiring further investigation.
The instrument cluster displayed an emissions warning stating that starting would become impossible in 600 miles, making it important to identify the underlying cause before the countdown progressed further.
Modern SCR emissions systems contain several interconnected components. A warning message or stored diagnostic trouble code does not necessarily identify the component responsible, so accurate testing is essential before recommending repairs.
Initial diagnostic assessment
Multiple faults stored within the SCR system
We began by carrying out a full vehicle diagnostic scan. The engine control module contained several faults relating to the reductant and AdBlue system.
The recorded faults included:
- P208E – Reductant Injector Performance – Stuck Closed
- P20A2 – Reductant Purge Valve Control Circuit Low Voltage – Low Signal Amplitude
- P20E8 – Reductant Low Pressure – Low Signal Amplitude
With faults pointing towards several areas of the SCR system, replacing components based only on the individual fault descriptions would not have been an appropriate diagnostic approach.
Diagnostic investigation
Tracing several DTCs back to a common fault area
Further testing of the SCR and AdBlue delivery system was carried out to determine why several related faults were being generated at the same time.
Testing identified the underlying problem within the SCR pump and associated control unit. The fault was affecting operation of the AdBlue delivery system and was responsible for the multiple faults stored within the engine management system.
Multiple codes did not mean multiple failures
The stored DTCs represented different symptoms within the same system. By testing the system rather than replacing parts from the fault-code descriptions alone, the common underlying fault area could be identified.
Repair options
Understanding the design of the AdBlue system
Due to the design of the system, the affected pump and control components are not conventionally serviced as individual replacement items.
The conventional repair route would therefore involve replacement of the complete AdBlue tank assembly, including the delivery unit and associated control unit.
Once diagnostic testing was complete, the findings and available repair options were fully explained to the customer so they could make an informed decision on how they wished to proceed.
Final outcome
Diagnosis completed before repair decisions were made
The most important outcome was that the Grandland X left the diagnostic process with the underlying fault area identified, rather than components being replaced solely in response to individual stored fault codes.
By considering the relationship between the multiple DTCs and testing the SCR delivery system itself, MPH Northwest was able to identify the common problem and provide the customer with a clear explanation of both the fault and the available repair options.