I have a 2023 TLX with SH-AWD and I have been experiencing intermittent AWD warnings since 9651 miles (approximately 8 months of ownership). The warning stated "All Wheel Drive System Problem. Only Front Wheels May Be Powered. See Your Dealer.", with the AWD light illuminated. The car drove with front wheel power only, but was otherwise normal. After restarting the vehicle, the error goes away and the car drives normally with AWD.

I was not able to reliably reproduce the error. Most of the time it was when accelerating from a stop, regardless of throttle input or drive mode. I was able to activate the warning intentionally once by accelerating normally from a stop and letting off of the gas before the transmission shifted from 1-2. But I was not able to repeat that again. From what I could tell, the warning activated near or on a shift most of the time.

After 9651 miles, the next warning was at 13977 miles. I've had at least a dozen activations of this total but I've recorded it at 9651, 13977, 14441, 14525, 14824, 14852, 15655, 15663, 15852, 15934 miles. I've had one differential fluid change (per the maintenance minder) and that made no change. I've brought it to the dealership for diagnosis at 14824 miles. They were able to pull the stored code, C1844-62 Right Diff Fluid Pressure Deviation. They were not able to proceed with diagnosis until the code was live, so I returned at a later date. The second visit, the differential fluid was replaced and the left and right pressure sensors were swapped to try to rule out sensors. I was told to come back when or if the warning came up again. The warning occurred again, and the third visit the code stored was still the right pressure deviation, so it was determined the rear differential would need to be replaced.

Carrier Assembly, Rear Differential 41200-59H-000 was replaced under warranty to fix the issue.

 

Excellent write up and textbook example of how to work with your Dealership to resolve a difficult-to-diagnose problem. Your concise documentation and patience should serve as a reminder to all of us that we car owners (as the one who should best know the car) have an important role to play in the process. To me it's not enough to just bring the car to the shop and say "Somethings wrong...Fix it". Instead, your documentation gave the technician a crucial head start in the troubleshooting process. Well done in all respects, Sir!