Trouble codes 37 and 51

I ran a check on my 980 w150 with a 318 and got a 37 and 2 code 51's. IK did it twice ans code 51 came up twice on the same scan. It read 12 37 51 51 55. Does anyone know why 51 would come up twice? Also code 37 is "part throttle unlock solenoid circuit is open or shorted". Does anyone know what that means? Thanks