i believe there are two solenoid switches in the SLA Shift Lever Assembly; The BTSI and the Park Reverse Interlock. The BTSI prevents the shift lever from moving out of Park unless the brake peddle is depressed and the Park Reverse switch/solenoid prevents shifting the lever into park or reverse when the car is moving above 5~6 mph. The park neutral switch is located on the solenoid plate in the transmission. The OP has not mentioned being unable to move the shift lever out of Park.
I think until he gets a better scan (assuming it isn't the RCM, see post post #8) it is just a guess as to what the problem might be. The SLA could certainly be the cause of the problem.