OBD-II Code P2646 is defined as a "A" Rocker Arm Actuator System Performance/Stuck Off
The Rocker Arm Control Solenoid supplies hydraulic pressure to the Variable Timing mechanism. This allows the Variable Timing System to adjust valve timing as needed. The engine's control module (PCM) uses the Rocker Arm Oil Pressure Switch to verify correct oil pressure for proper activation of the Variable Timing mechanism. If the PCM does not see the correct voltage signal back from the Rocker Arm Oil Pressure switch, the PCM will set code P2646.