2018 F150 5.0L Lariat I am not getting vacuum to unlock the IWE's when in 2 wheel drive. I have vacuum at the solenoid, I have 12v at the solenoid, however it doesn't work. I have tried 3 solenoids, so it is not that. If I shut the truck off, the solenoid clicks and it allows vacuum to the IWE's. Once I start it, the solenoid does not work. Has anyone had a ground problem with their IWE solenoid???

 

The 12v is there constant, the ground switches active low to enable the pass through of vacuum. Your 2018 F150 will never pass vacuum until it is actually driven more than 1/2 mile, giving the vacuum canister time to achieve proper vacuum levels to pull the IWE smoothly without chatter.