LI49-20-N-080376

The check engine light is illuminated, or the AdBlue warning is active, with recorded faults related to AdBlue quality or concentration. Complaint Customer reports an illuminated check engine light and or an AdBlue system warning indicating AdBlue quality out of specification. The vehicle may enter reduced performance mode. One or more of the following fault codes related to the AdBlue tank may be stored: P206B31: Malfunction of the concentration sensor for AdBlue; the signal is absent. P203B31: Malfunction of the AdBlue fill level sensor; the signal is absent. P300494: The quality of the AdBlue is insufficient. Background AdBlue must meet ISO 22241 quality requirements. ISO 22241 urea content limits for AdBlue are 31.8 percent to 33.2 percent by mass. AdBlue begins to crystallize and freeze at approximately 12 degrees F. Freeze-thaw does not degrade the product when uncontaminated, and the bulk concentration returns to normal after complete thaw and mixing. Cause In cold soak conditions and during freeze thaw exposure, the tank contents may not be uniform at the time of sampling or system checks. During freezing and partial thaw, ice formation can temporarily create concentration gradients in the tank. As a result, urea percent readings can vary based on sample location and the state of thaw and mixing, which can produce apparent out of range readings even though the bulk fluid returns to normal after mixing. Remedy Testing Do not use a single urea percent reading taken from frozen, partially frozen, or not fully mixed AdBlue to make a repair or responsibility decision. Confirm full thaw and ensure tank contents are mixed before sampling. 1. Confirm full thaw - Confirm the AdBlue tank and associated components are fully thawed before sampling. - Do not sample slushy or partially frozen fluid. 2. Mix tank contents - Perform a road drive intended to mix the tank contents before sampling. - Idle time alone is not a reliable substitute for mixing. 3. Sample and measure - Take the sample and measure with the MB refractometer per the MB tool instructions. - Record the urea percent value. 4. Interpret the result against ISO 22241 limits - Within specification is 31.8 percent to 33.2 percent urea by mass. 5. Repeat if out of specification - If out of specification, repeat after an additional mixing drive to reduce sampling variation. - If still out of specification after full thaw, mixing, and repeat measurement, treat as a true out of specification result and proceed with further diagnosis per applicable MB guidance. Acceptance criteria AdBlue is within the ISO 22241 specification when the urea percent is between 31.8 percent and 33.2 percent by mass. Values outside this range are out of specification and require further diagnosis after completing the full thaw and mi-xing procedure above. Cross reference For vehicles with fault codes P206B31, P203B31, or P300494, refer to LI49.20-N-078838 for the detailed diagnostic and repair procedure. If a SCR or AdBlue warning reset is required after correction, refer to LI49.20-N-075995. Complete the diagnostic and corrective steps first. Perform the warning reset only after the underlying fault condition has been corrected. Warranty information and claim handling