1999 Ford Ranger XLT 4x4, 3.0 flex fuel. 107,000 miles. I have error codes P1832 and P1878, both related to solenoid failures for the transfer case, one for lock-up, one for disengage solenoid. When I switch from 2WD to 4WD -High and then to 4WD-low, the dash lights come on and the transfer case motor clicks in and I can tell 4WD is engaged when I drive it, but the error codes are still there. I've checked all the vacuum connections and electrical connections and can't see anything amiss. I did have "check engine" light but took care of that with new DPFE sensor, which is also vacuum driven. Replace the solenoid that's behind the right side headlight?

 

P1832 Transfer Case 4WD Solenoid Circuit Open/Short To Ground
P1878 Transfer Case Disengaged Solenoid Circuit Failure

There are no solenoids used in 1983-2011 Ranger 4WD transfer case system
Just an electric motor(same as power window motor) and 4 contact switches for position

1998-2000 Ranger did use PVH front locking hubs, but it uses a vacuum valve to pulse vacuum to front hubs when 4WD is activated and Ford did call that a "solenoid" in some manuals
Have a look here: https://www.therangerstation.com/tec...oubleshooting/

The lights on the dash are just to show that the shift motor has has moved transfer case's shift rod into the correct position, but nothing to do with front hubs being locked or unlocked

So the codes could only reference the PVH system that locks and unlocks the front hubs

 

I had read that link earlier that you posted. I don't just see lights on the dash, I can feel that 4WD is engaged in both high and low. I'm going to replace the "solenoid"/switch that's behind the right head light and see what happens. I'm hoping the GEM isn't the culprit and sending false error signals. I also have error codes for the power windows and they work just fine!

 

FYI I replaced the "Pulse Vacuum Actuator 4WD" that's behind the passenger side headlight and under the air box base..............voila! Everything works and no error codes, at least not those two (P1832 and P1878)!!