OBD-II Code Transmission may not shift properly is defined as a Pressure Control Solenoid "A" Control Circuit Range/Performance
The Transmission Fluid Pressure Solenoid allows the engine's control module (PCM) or Transmission Control Module (TCM) to use hydraulic fluid to engage the clutches in the transmission to allow for smoother shifting while driving. If the PCM or TCM detects an issue with the electrical circuit to or from this solenoid, the PCM or TCM will set code P0961.