Mercedes-Benz bulletin LI28_00-N-079097_1_en

Complaint While driving through muddy / sandy/ off road terrain "4Matic Currently Unavailable" message on the dash Cause This vehicle is not equipped with a fixed force distribution AWD, rather force is only applied to the front axle according to ESP calculations. As per GF28.00‑D‑ 9900A: "vehicles with 4MATIC all‑wheel system and variable force distribution, an electronically regulated multiplate clutch integrated into the transfer case provides for the torque distribution. If the multiplate clutch is open during normal driving operation, only the rear axle drives the vehicle. If the clutch is closed, the front axle comes into play." The message "All‑wheel drive temporarily unavailable" is not indicative of a malfunction but rather informs the driver that all‑wheel drive is currently not available due to the transfer case clutch overheating. This occurs when the vehicle is driven in such a way that maximum front axle torque is needed for an extended period, causing the clutch to get excessively hot. If the vehicle is being driven under heavy load conditions, like in deep sand or snow, the rear axle may slip while the front axle does not deliver power. The transfer case then attempts to distribute torque to correct the slip, but it is limited to a maximum of 1150 Nm to protect the front axle transmission. In extended heavy‑load scenarios, the multidisk clutch in the transfer case slips, increasing the temperature. If the temperature model detects a critical temperature of 240°C, the system protects itself by disconnecting until it cools down to around 160°C, after which the all‑wheel drive becomes available again and the warning message disappears. Vehicles can handle flat terrain easily, but steep slopes or situations where wheels slip might cause additional resistance, leading to the described protection events and message in the dash. Remedy Recommendation is to release the vehicle back to the client with an explanation that the vehicle is operating as designed. Please advise the client to limit vehicle acceleration in limited traction situations to avoid disabling of the 4Matic system ‑ please see "Notes on all‑wheel drive" provided in the operators manual.

Owners of the 11 model years this bulletin names have filed 547 complaints with NHTSA since 2015. 75 of them name Power Train — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.

On the 2019 Mercedes-Benz Sprinter, the 14 owners who gave an odometer reading for Power Train reported it at a median of 24,000 miles. That figure is one model year’s, not the whole range this bulletin covers — medians from different model years are not averaged.