I've done a number of searches and I haven't seen my problem described. I have been chasing the open 4x4 solenoid codes in my 2004 F-350 King Ranch 6.0 DRW. The HVAC and ESOF were working perfectly. I read where someone replaced the PVH solenoid and the codes went away. So, I ordered a Ford PVH solenoid from RiffRaff. I installed the new PVH and the codes went away, but this is where it gets weird. When I switch from 2wd to 4wdHi the HVAC switches from the vents to the defroster. After about 45 seconds to a minute it switches back to the vents. Also, I do not think the hubs are locking. I do get 4x4 on the dash.

I've used my Mityvac to draw 10inHg vacuum on the front hub vacuum line that terminates at the PVH solenoid. It holds vacuum. I then pulled 15inHg on the HVAC vacuum line and it holds vacuum. I then pulled 10inHg on the storage tank and it holds vacuum. Sitting still KOEO, if I switch from 2wd to 4wdHi the vacuum pump immdiately comes on and runs for 45 seconds to a minute. I also ran 12 volts to the center pin of the new PVH solenoid and then grounded each outer pin. I heard a click and vacuum being released.

So, is my vacuum pump weak or is the new PVH solenoid bad or something else?

 

Check for codes.

 

Codes P1876 and P1832, the ones I thought I got rid of, are back.

 

Just spit balling here…..the hubs use a pretty intricate expensive seal to hold the vacuum that locks in the hubs. Perhaps you’re not losing vacuum until these seals are turning. You could cap each side individually, clear the codes and go for a drive see if anything improves. My be an easy test to eliminate the hubs altogether.

 

Did you get an Aftermarket solenoid or OEM?

 

I replaced the hub seals with the correct special tool a couple of years ago. 4x4 worked until I installed the new OEM PVH solenoid from RiffRaff. Actually, I think 4x4 worked on my first test drive after installing the new PVH, but I got the defroster problem so I started trying to track down vacuum leaks. Next test drive, I don't think 4x4 was working, but I am not sure. Steering feel changes on my truck when the front hubs lock and it didn't seem like it changed. I am going to go into the pinpoint tests for the two codes and see what I find.

 

Turned out that the new OEM PVH solenoid was bad. Leaked every time it was engaged.