I have a 2000 F-150 XL with a 4.2 V-6, a 5 speedmanual transmission and manual shift on the fly transfer case. The 4WD went outover a year ago. When it went out, I was driving at 65 MPH and heard whatsounded like rapid relay chatter for several seconds (10 to 15 seconds) and itstopped. The sound seemed like it was coming from the dashboard area where theGEM is located, but may have been from the solenoids mounted on the enginecompartment firewall. Actually could have been from both. When the 4WD tried toengage while driving at 65 MPH, the dash lights were flashing on and off and itsounded like the front differential was trying to engage. Of course I slowed downwhile this occurred to avoid damaging the truck should it succeeded to engagethe front differential.


I have a Haynes manual but the wiring diagrams aresomewhat ambiguous as my truck is not as common as those having ESOF. Evenresearching online I am not certain if the info pertains to my truck. The onlydiagram I found to be accurate is the vacuum control diagram. I believe I haveeither a wiring problem or the GEM is bad. When troubleshooting I like toisolate at the middle points to quickly eliminate one side or another whenlooking at a diagram/schematic.


Ford had a well-noted problem with the two solenoidsthat control the 4WD actuator and are mounted on the engine compartmentfirewall. So I started here, as this is a good halfway point and high failure area.Well, the solenoid power connectors had 12 volts on both connector pins (if Iremember correctly as it was a year ago when I did some troubleshooting)regardless of transfer case shift position (2wd, 4wd high or low). I was ableto manipulate the solenoids and verified they were operating, as I could feeland here the solenoids click when grounding the control side of the pin on eachsolenoid. I did check fuse 23 prior to checking the solenoids. Since 12 voltswas present at the solenoids, it indicated power was getting to them.


So another common problem is the transfer case 4WDsensor. I removed, cleaned, and verified operation of the sensor. Reinstalledand check sensor state with transfer case in all 3 positions and it was workingcorrectly. Also I have no 4WD indication on the dashboard when 4WD high or lowis selected. Fuse 6 is good.


My main issue is not having confidence with thewiring diagrams I have found online. I am not sure if my truck has a MSOF relayor the transfer case 4WD sensor signal goes directly to the GEM.


I need to check:


1. Wiring from transfer case 4WD sensor to eitherGEM or MSOF relay, if there is a relay, will check it along with wiring to GEM,but don’t believe it exists for my truck.


(I NEED THE WIRING DIAGRAM TO DO THIS)


2. If the transfer case 4WD sensor output is gettingto the GEM module, I would think the GEM module is bad. If possible, I wouldlike to check the GEM module outputs to the solenoids, but since the GEM isburied behind the fuse panel, it probably is not feasible.


I plan to call the Ford service department in myarea to determine what GEM I have and will buy a GEM online. Replacing the GEMdoes not look fun, so I have avoided it but wanted to be sure it was theproblem.


So I want to know if I am tracking correctly and ifthere is anything else I should check, and would like the correct wiringdiagram as indicated in item 1.

 

Your looking at the wiring and its is probably not that.. Since you have a MANUAL transmissison, I assume you have a MANUAL 4 x 4 ? There is a shift lever on the floor for moving from 2 x 4 to 4 x 4 ? If so, that cable goes from the shift lever to the side of the transfer case. Check both ends to see that the cable is moving full travel. If so, and you don't get the front driveshaft to engage, you probably have an internal transfer case problem.......... If you have a selector switch on the dash for 2 x 4 to 4 x 4 , then the signal goes to an electric motor on the side of the transfer case. Pull the motor off and test it for proper operation and full stroke. ..... the dash lights only work when the shift moves FULL STROKE.

 

who ever told you the vacuum solenoids and the dash lights were a major problem, does not know the system. FIRST thing to do is see if the transfer case moves full stroke and engages the FRONT DRIVE SHAFT.. Second is to see if the vacuum moves the FRONT AXLE ENGAGE piston.......... you know you have vacuum from the solenoids to the piston ( cylinder), but you didn't check that the cylinder is engaging the axle ?

 

First off, did your read the stickied thread at the top of this section, the one that says "Read First: How to Troubleshoot and Fix F150 4X4 1997-2003 "? That thread has a LOT of information in it (as well as a lot of noise and chatter) as to how the 4x4 system is diagnosed and how it operates. However, a quick scan of the posts indicates they're pretty much for the ESOF version and your MSOF is a bit different.

Attached are the factory documents for the MSOF, they should provide you with the specifics of your version. I've also included some background info on the ESOF system so you can better correlate the available online information to the specifics of your version, should there be any correlation.

 

I have read most of the 4wd posts and since my truck is a fully manual actuated transfer case, the first two responses to my post are inaccurate. I do not have a dash switch. The sensor located on the external part of the transfer case which is really a switch is changing state from 2WD to 4WD. I believe it was open for 2WD and closes when shifted into 4WD. I thought I described what happened in my post while driving and how the 4wd went from working to not working. This is why I thought the GEM was the likely issue. When driving one day at 65 MPH, the 4wd tried engaging several times and then abruptly stopped. A relay or solenoid chatter along with dashboard indications the truck was trying to engage 4wd was also noted. The truck has a manually activated transfer case, no dash switch or any transfer case magnetic clutch coil
.

 

Thanks for the schematics, but this is what I have found too. I must have a rare truck as my transfer case is old school, no magnetic clutch coil.

 

Yes, I have a MANUAL 4 x 4 and there is a shift lever on the floor for moving from 2 x 4 to 4 x 4 ? There is no cable, it's direct linkage from the transfer case to the 4wd shifter. There is no dash 4wd selector switch and no electric motor on the side of the transfer case.

 

The vacuum solenoids were known to have issues due to water intrusion. Well known problem.

 

The schematics I provided are the FACTORY documentation for the MSOF. If you have something else, it's not factory and you'll have to figure it out on your own.

Good luck.