First response: Try using the system more. Sometimes something gets a little "sticky" from non-use/cycling.

Secondly: Has the truck been in a lot of water recently? Mine gets a little wonky after a lot of water crossings or cruising through large mud puddles, but it clears up after it dries out.

Somewhere on here, there is a link to a big write-up on how the system works, and it's surprisingly complicated, but the article takes you through the how's and why's before getting into a step-by-step diagnostic. Does anyone know where to find it (obviously, I type before I look)?

John B.