1999 Expedition XLT no 4wd please help

Hey thanks for the posts and suggestions, i finally got time to do some diagnosing last night. Also got some questions answered but made more, i swear that’s how it goes. Right now the truck does have the 4×4 light on the dash Front Hubs are locked in and transfer-case is in 2h. (front drive shaft is spinning while moving) When i pulled the motor of the Transfer-case i can ad power to it and it does spin, so i put the transfer-case on 4h spun the motor to the 4h position (using the power probe 3, wonderful tool). Then i bolted it back up hooked it all up left the switch on the dash to 4h, Once i turn the key i heard the motor spin back to 2H (pulled it off and looked). Now when i try to change the switch to A4WD it just clicks clicks like it’s trying to spin the motor to 2h even though its on 2h the motor can not spin any further so it just gives up. When i change it to 4l i get nothing. Now is it the sensors in the motor that have failed or could it be the GEM module, i don’t think it is the switch cause it reads right on the Resistance I hope that was some more information and not to much rambling, look forward to your advice again, thanks.

Hey thanks Eric for the post love the videos and advice, that’s where i get most of my diagnostics ideas from now :), Was wondering on when you said linkage cause at the moment i have the transfer case motor on but turned to 4h on the transfer case with the fuse pulled. Cause every time i turned it to 4h with the switch on 4h it would change back to some where between 4h and 4l, then back to 4h on A4WD, never to 2H. Been getting confused and its been to darn cold (-20 with wind chill) to do any thing out side i need your shop..lol. To bad i live in Northern Nevada. One thing i did read about this from the post that one guy made was that it could be the sensor in side the motor telling the computer where the motor is spun too, im kinda leaning that way but did want more info from you before i spend money and freezing my but off outside..lol One more thing about the 4Wd not being used a lot it kinda is since it is a Auto 4wd meaning when it gets rear wheel slip the 4wd kicks in which did work, tell it broke..lol, thanks again hope to hear from you again when you get time.

Thanks again Eric, there is sensors in the motor and i am think that is what is not reading right, so the Computer is not sure where the motor is, when i get the time and the weather to replace it i will let you know how it went. Why do things have to break in winter..lol. As of right now i have it locked into 4wd and its working but i know its not good for it past 55mph so yeah weather permitting hoping to get to it soon, thanks again

Sorry for such a late response on this topic, just wanted to update anyone that may have been tracking this. I bought the transfer case motor about a month ago. That being said once i swapped the motor out, which you have to transfer wires from the speed sensor mounted to the transfer case. Which i just unbolted it all off the transfer case which was the easiest way to go, instead of being under the truck. I have determined it was the motor even though the motor was good but the sensor that are in the motor assembly telling the PCM where the motor is at (2H, 4H, or 4L) failed. Now that i have the motor swapped and all wires and sensors mounted correctly the A4WD, 4H and 4L works like brand new with no more flashing 4×4 light or other issues. So thanks for all the input and if any one else that has the same year of Expedition or with just the A4wd i hope this may help you out. One last note the part i got was dorman 600-802 $65.41 from amazon, and with basic socket wrench with 3″ extionsion and 10mm socket and truck on ramps took me less then 2hrs. So this concludes this issue SOLVED! banana: