We've had 4 instances of "engine power reduced" and check engine light, with no prior warning of issue on the dash display. I believe this is due to an issue with the diesel particulate filter soot load tracking. The first 3 occurred on rural highway and the 4th on a local highway at speed. The power reduction is immediate and severe enough that the vehicle rapidly loses speed and cannot keep up with traffic. Had traffic been close or with a trailer, there would be risk of being rear ended due to the sudden loss of speed. I feel there should be some warning to give a few seconds even to put on hazards and prepare. The last two events had code: P2463, the dealer ran a service regen, but no fault was found. On the last one, the dealer gave me GM service bulletin #10-06-05-002G stating the GM would no longer cover the service regen under warranty for P2463 with no fault found. I the purchased an obd reader to monitor the dpf soot load and observed erratic behavior in the soot load, with 2 instances of the loading jumping over 100%, but apparently not enough to trip the check engine. I then contacted GM customer service to Express my concern and share the data, the dealer then ran additional tests under GM's tech guidance, but in the end GM states that they could find nothing wrong and the vehicle is operating as intended. I've attached the service records. The last record shows the dealer incorrectly listed my concern. My communications with GM customer service have all been phone calls.

- Hopewell, IL, USA