Information relating to Mercedes AdBlue and SCR system faults, including common warning messages, NOx sensor issues, and diagnostic considerations.
Some Mercedes vehicles may display an AdBlue warning stating that the AdBlue level cannot be determined, even when there are no previous engine warning lights, SCR faults or restart countdown warnings stored.
In these cases, live diagnostic testing is required to identify faults within the SCR system, including possible NOx sensor, AdBlue level sensor or control unit communication issues.
Accurate diagnosis should always be carried out before replacing components or considering further system repairs.
Unauthorised removal or modification of the AdBlue / SCR system may result in additional fault codes, warning messages and emissions compliance issues. Correct diagnostic testing should always be carried out before replacing components or attempting system modifications.