You unplugged the connector shown in your picture and can still engage?  I'm guessing the wires in that bundle are shorted together somewhere.  Maybe where it enters the cab?  Good news is that you don't have to buy a new flow switch.  Bad news is it will probably take more work to find exactly where the problem is.  Basically need to look for damage to the harness. 

You could also try checking continuity between the pins in that plug on the end of the cable.  There should not be continuity.  You can also check voltage, one should have voltage, the other should not.