DTC P1889-14: Oil Pressure Pump Performance - Circuit Short To Ground Or Open: Action

Using the manufacturer approved diagnostic system check and install latest relevant level of software to the rear differential control module
Carry out visual check of the cable and connector between oil pump and the rear differential control module
If no circuit faults exist clear the DTCs and retest. If the fault persists install a new pump as required. For additional information, refer to: Active On-Demand Coupling Oil Pump