I have a 2006 f150 I noticed recently that someone had plugged off the vacuum lines to the actuators, did some testing and found that the passenger side was stuck in the engaged position. I replaced the actuator and connected the lines but now I can't get them to engage when I shift to 4 wheel, they have a vacuum to them all the time despite the position of the shift lever. If I disconnect the lines they engage like they should, What could cause this issue?

 

Probably a faulty IWE control solenoid.

 

Its up on the firewall. Fordtech Makuloco has a vid that explains how to check it on youtube.

 

 

That's what I was thinking, just wanted to check if there could be something else.