Hey folks, I've been scratching my head on this issue for some time so maybe one of you guys can help shed some light...

I have a 98 F150 4x4 with ESOTL that isn't engaging in to 4WD HI or LO. I am not getting any dashboard indicator lights or any audible clicking from the sound of a relay either. I have also tried this with the truck in motion and also in neutal.

I had just pulled the instrument cluster apart to replace several burnt out bulbs a few days ago when I discovered this problem. I actually had my attention drawn to the 4wd switch because it wasn't illuminated (the wife drives the truck most of the time so I didnt even recall if it did light up). After inspecting the switch I saw that it did have a bulb so I tested for voltage going to it. I was able to pull a solid 12v over the outer two contacts of the plug (with the lights on) and verified that the bulb was indeed burned out, but the 4wd is obviously the bigger issue here.

For starters I pulled each fuse from the drives side fuse panel and did a visual inspection of each, I also disassembled the 4wd switch and noticed the 3 resistors within and tested the resistances of each. With the switch put back together I was getting the proper impedences from the center two terminals. From what I gather from the Haynes manual the 5v signal voltage goes through the resistors and that tells the GEM where to shift the transfer case. Since I'm getting 5 volts at the plug and the switch seems to be doing its job I'm not sure where to troubleshoot next.

Just for the record I am not sure if the 4wd was working prior to me pulling the dash apart or not since it's not my daily driver. The wife claims that she used it probably a month ago with no issues. Also, since I'm stuborn and always figured disconnecting the battery cable was for wusses, I did all this with the power on! There weren't any crackles or pops while I was putting the dash back together, so I'm pretty sure I haven't shorted anything out.

Any help you guys could offer would be most appreciated.

 

The illumination circuit in the mode selector switch is a different circuit, so you have ID'd the burnt out bulb.

The not shifting into 4WD hi or lo ( not sure if both or either ) is usually a bad vacuum actuator / diaphragm on the front axle, most of the time.

Might want to take a search here for the same topic ( at least 3 in the past 45 days, same MY range 97-98 ).

Here are 2 of the threads. 1 was a GEM problem, the other the vac solenoid
https://www.f150online.com/forums/el...ipers-etc.html

https://www.f150online.com/forums/el...-problems.html

Confirm the vac operation prior to digging too far.
The reason the 4x4 indicators might not be illuminating on the cluster is the front axle might not be engaging, and the feedback to the GEM on the position is what causes the lights on the cluster to illuminate.

Too many times the problem is mechanical, and the GEM functions lead people to an electrical issue.

Just some ideas to think about, not saying it is not an electrical issue, but check the mechanical operating first, and take a look in the other power train forum for more mechanical pointers. JMC hangs around there and the engine & 1997-2003 forums, and knows a ton about the 4WD functions ( as well as electrical )

 

Well I am still battling with this 4wd problem. After doing some extensive reading on the topic, I was pretty convinced that my problem lied with the transfer case shift motor. In the interest of not buying any unneccessary parts, I bit the bullet and took the truck to the dealer for a diagnostic to verifiy I wasnt having a GEM issue. $120 bucks later the dealer said it was my shift motor and they couldnt press on until they changed it. I respectfully declined their overpriced service and picked up a new motor from NAPA for $125 and installed it myself.

Unfortunately with the new motor installed my problem hasnt gone away. Researching further, I rechecked for continuity over all the vehicle fuses underdash and underhood at least 3 times. I have tried to pull voltage from the actual transfer case motor plug coming from the truck to see if any power was available to the motor, which there was none. The tech I spoke to at the dealer said there should be at least one terminal in this plug with 12v all the time, but i couldnt locate it here. This is leading me to beleive there is something amiss electrically.

I handed the truck over to a friend of mine who is usually a wiz at finding thses wierd problems and he walked away scratching his head. While he did have the truck he noted some wierd electrical issues like the door not chimming with the door open and the key in the ignition and some other odds and ends. As I was standing there, he pulled a fuse out of the box while the truck was running (presumably the one that controlls the door chime) and then the 4wd light suddenly came on. I tried to disengage it with the switch but was still getting no response from it. To verify that the truck wasnt stuck un 4wd, we placed the entire truck on jack stands and put it into gear. The back axle was spun, but the front didnt budge.

This is especially strange because the light shouldnt come on unless the transfer case motor isnt in the right position! I spoke with a dealer tech on this situation a bit and he suggested that I unplug the motor to see if the light goes out in the dash since it is supposedly part of that circuit. I did this and its still on. Later today I will try to do the battery disconnect trick again to see if this resets anything. The only other avenue I can think to look at is to inspect the GEM terminals for corrossion and possibly replace.

You guys have any other suggestions for this stinking issue?

 

Found the problem! I had a cut wire in the drivers sider rocker panel that was part of the shift motor harness. I repaired the wire, disconnected the battery for 10 minutes and took it for a spin. It took the truck being started and stopped serveral times, but it eventually relearned the shifting pattern and eveything is working as advertised!

 

That wire bundle seems to be the cause of a multitude of problems, doesn't it? There are numerous posts on broken/frayed wires in this location causing all kinds of weird symptoms. Almost seems like this is the first place to look if things start going bad.

Good post, kovedawg! Thanks for letting us know the cause of the problem.

- Jack