LI49-20-N-078838

Check engine light or Adblue warning with fault codes P206B31, P203B31, or P300494 present in AdBlue (SCR) control unit (N118/5) Complaint The check engine light or AdBlue warning is activated, accompanied by one or more of the following fault codes related to the AdBlue tank: 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. Cause A. The software for the AdBlue (SCR) control unit (N118/5) is outdated. B. The AdBlue concentration is outside ISO 22241 limits (below 31.8 percent or above 33.2 percent). C. Frozen or partially frozen AdBlue can cause the AdBlue level and concentration functions to report inaccurate values. D. The AdBlue level and concentration sensing functions in the tank are damaged. E. Cold soak and freeze thaw exposure can temporarily create concentration gradients in the tank and lead to sampling dependent readings until fully thawed and mixed. Important Before evaluating any AdBlue concentration result, follow LI49.20-N-080376 to confirm full thaw, perform a mixing drive, and retest. Do not use a single urea percent reading taken from frozen, partially frozen, or not fully mixed AdBlue for a repair or responsibility decision. Remedy A. Software 1. Verify no newer software is available for the AdBlue (SCR) control unit (N118/5). 2. If a software update is available, program the control unit per XENTRY guidance. 3. Only after the system is in proper working condition, complete LI49.20-N-075995 for AdBlue warning reset. Note: If there is no updated software available, print the XENTRY screen indicating this and proceed to section B. B. AdBlue concentration 1. Confirm full thaw and mixing per LI49.20-N-080376, then verify AdBlue concentration. a. Check concentration using the MB refractometer per the MB tool instructions and applicable WIS guidance. b. Use freeze frame data when applicable. 2. If AdBlue concentration remains below 31.8 percent or above 33.2 percent after full thaw, mixing drive, and retest, AdBlue replacement is required. Warranty and responsibility decisions must follow LI49.20-N-080376 warranty handling guidance and standard war-ranty policy. 3. If AdBlue concentration is within specification, proceed to section C. C. Frozen AdBlue or SCR actual values indicate frozen AdBlue 1. Check if AdBlue is frozen. If frozen, allow the vehicle to sit in a warm environment overnight and recheck. 2. With the vehicle running and XENTRY connected, display the actual AdBlue level values. 3. Drain the AdBlue tank and verify the displayed fill level reflects the change. 4. Fill the AdBlue tank slowly. Do not overfill. Verify the fill level reflects the change. Note: For model years 23 to 25, Fill Level Sensor 1 functions as the empty sensor and accurately measures only the bottom portion of the tank. Once the level is above the measurement range, the displayed value may fluctuate. This is nor-mal. 5. Reset the AdBlue tank fill level via XENTRY. Print the XENTRY pages showing that the fill up completed success-fully. 6. Only after the system is in proper working condition, complete LI49.20-N-075995 for AdBlue warning reset and print the XENTRY pages confirming the reset completed successfully. Note: If XENTRY still indicates frozen AdBlue or the concentration remains inaccurate after drain and refill and the thaw, mix, retest requirements were completed, proceed to section D. D. Damaged AdBlue level and concentration sensing functions 1. Replace the AdBlue tank as required by applicable MB guidance. 2. With the vehicle running and XENTRY connected, display the actual AdBlue level values. 3. Fill the AdBlue tank slowly. Do not overfill. Verify the fill level reflects the change. 4. Reset the AdBlue tank fill level via XENTRY. 5. Only after the system is in proper working condition, complete LI49.20-N-075995 for AdBlue warning reset.