My 2002 5.4L Screw will not engage in 4wd. After researching many threads, I decided to test for a switched ground at the solenoid connectors first. I unplugged both connectors and placed my 12vdc trouble light on the connector closer to the passenger side first. With ignition on and switch moved from 2h to 4h the light came on, but did not go out when switched from 4h to 2h (even after about 20 seconds). I turned ignition off and trouble light went out. I then moved the trouble light to the other solenoid connector(closer to the driver side) and turned ignition switch on. The trouble light immediately came on. When I switched from 2h to 4h the light stayed on. This seems to indicate that this solenoid would be engaged constantly. Should I be looking at the GEM module next? Any help is greatly appreciated.