Hello I saw your post and just have a few questions. I am new to this forum and I have a 1997 F-150 XLT 4.6 Liter with "W" code engine with shift on the fly shift **** control. My 4x4 hasn't worked for a while and I have been throwing parts it it and still don't work. The symptoms I have is that the 4x4 high and low lights come on when I turn the key to start the truck in the instrument panel. But when I turn the switch Electronic shift on the fly switch to any position to engage the 4x4 nothing happens. I hear the relay module click a couple of times but nothing happens as-far-as the enguaging into 4WD I have installed a new transfer case shifter motor, new vacuum actuators on the firewall Both have been replaced. new vacuum actuator on the front transfer case, and a New GEM Module I been looking for a transfer case shift relay but cant find one. My part number is F75B-14B194-BC I can't find this part number. I can find the same part number but the all end in AC,CA,BB and mine ends in BC does this part have to be exactly ending in BC and can you please tell what these abbreviations means for my educations purpose.

 

Have you checked to see if you have a vacuum leak?

If you search on here, there is an extensive list of checks you can perform BEFORE throwing parts/money at it.

 

There are no relay modules unless they are from a used parts source.
I get very reluctanrt to try helping anyone who does what this poster does without any thinking about how the system works, what point it stops, or indicate doing any testing.
This reply likely will not be well recieved but it is what it is.
Imagine if his Doctor or a mechanic worked like this?.

 

I have to agree with you Bluegrass. We all get tired of trying to solve problems for people that have been throwing parts at their problem and now have most likely made the problem worse by replacing working parts with new BAD parts, messed up wiring connections, blown fuses and possibly shorted other things out, and so on and so forth. I'd much rather try to sort out a problem that no one has SCREWED with. With an original problem, you can generally assume that there only ONE failed part but with something that someone else has been throwing parts at, there could now be MANY.

I hate dealing with people that want to work on their own vehicles but won't even buy a manual or go learn how the various systems on it work. There's really no excuse for it, manuals are available online or on E-bay and there are many You-tube videos and websites that explain how the systems work.

OP, not singling you out. This is the kind of things we deal with just about everyday. FWIW I have a 2010 and I know how the 4wd works on it but I don't know if your's is the same. But I've posted on here several times about how to manually shift the X-fer case and about the electronic shift motors and the problems that they have. You need to go read those. If your system is similar then the shifting problem is almost certainly the motor and not in the dash.

Edit to add: On the 2010s and similar systems, the vacuum has NOTHING to do with shifting the Xfer case. It's only used to lock or unlock the hubs and that can't happen until after the x-fer case shifts into 4 wheel low, so leave the vacuum system alone for now. You'll have to do some study to see if your model works the same but I expect that it does.

 

Joe, I believe the 2004+ system is different than the 97-03.

 

To try an education lesson becomes a long typing effort that may or may not be understood.
Your truck does not have "working hubs" but a single CV axles splined coupling action on the passenger side front axle, in the carrier case extension housing.. The actuator moves this spline when requested to do so by application or removal of engine vacuum to the Actuator by the firewall solenoids..
On 04 and later this is all different and involves vacuum at each front Hub. You have no vacuum lines to your front wheel areas.
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The hint of what is not happening is in the op disscription.
If 4H does not come on, the transfer case motor is not running to it's first position or the circuit board contacts are faulty. A function fault.
This is the stopping point of the fault. No use to be concered about firewall solenoids , front actuators etc if the system cannot get that far.
Hearing the relay modual clicking tells you the GEM is working at the request of the dash control 4H or 4L . No need to replace the GEM at this point.
The clicking is the GEM attempt to connect and run the case motor. It will try several times before stopping.
It's at this point the reason why has to be determined.
Is it an open wire harrness?
A connector issue?
Is it a fuse to power the motor?
Is it the fuse holder or blown fuse?
Is the case motor able to rotate or is locked up so it cannot move? It has to engage the case with the Transmission output shaft and operates an electric cone clutch to prevent gear grinding on the fly...
Hope you can see why repacing parts on a hope is just waisting money and generates frustration at failure plus possibility of adding more issues unknowingly..
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To make a point clear, the dash indicator 4H/4L is not nessesairly an indication the front axle has locked up. It only indicates the electrical and control system has functioned. In this case it has not.
Why? There is no provision the Actuator has operated as it is not electrical and there is no sensor to indicate actual lock up has occurred except the steering gets harder or not during turns, or improved traction has occurred...

 

I had the same issue on a ‘97 ranger and it was the actual on the fly switch on the dash

 

97 F250 (Medium Duty), 5.4l, 220,000 miles. New to the Forum. My 4wd ESOF system quit working. I took it to a 4x4 shop and they diagnosed a bad GEM module. 4 months later, it still wasn't fixed, he tried a couple of different GEM modules, no luck.

I take it to Ford. They refused to work on it and referred me to another local 4x4 shop. They did nothing.

I brought it home and began learning, making a few missteps along the way, eight months into it.

Let me try to describe the problem. First, when I start the truck, in 2wd, the first thing I hear is something clicking under the dash - it clicks exactly 6 times.
The shift switch does nothing.
I did check vacuum lines and solenoids - fixed what needed to be fixed, all appears ok. I did replace the GEM module. New GEM did not solve the problem. However, with t he new GEM, there is no clicking 6 times under the dash. When I put the new GEM in however, the 4wd light was on. Operating the switch did nothing. I was able to determine that the 4wd solenoid (on the fire wall) was being told to open the vacuum line to engage the front axle. Until I fixed leaks, that vacuum was weak, around 5 mm/hg. After fixing the lines, vacuum improved to 15 mm/hg.

None of this solved the problem however. I removed the transfer case shift motor. I found a Youtube video where the guy tested the control circuits in the motor, first with a good motor and then a bad motor. I tested my motor and found one of the four circuits was erratic - giving readings in the mega ohms. I also tested to see if the motor worked backwards or forwards on the bench. It didn't. I took that apart, cleaned the commutator, shafts, etc, lubricated the bearing cup, put it back to together, then tested the motor. It worked - but - I understood that if the circuit board controlling the motor was bad. So - I ordered a remanufactured motor.

Using the new GEM I installed the motor. NO DICE - nada. For giggles, I put the original GEM back in, I now get the 6 clicks just after startup, but nothing happens when I operated the ESOF switch.

I thought originally that the GEM was making the clicks. WRONG. I tracked that down this afternoon, and found the transfer case motor relay was the one clicking.

HOW can the relay be tested? I may also pull off the new shift motor and test it and see what it tells me. Any ideas or thoughts?

 

I did see some one posted on how the relay can be tested. I cant remember who it was I think it was a senior member of this site who showed how to hook up test leads to the relay.

 

The relay clicks several times in an attempt by the GEM to operate the case motor.
Obviously the relay operates if it clicks.
Next the case motor has to have power to run.
Drop the motor out still connected and see if it rotates to it's first position when you request 4H.
If yes the circuit board contacts may be worn.
If no, power is missing or the motor is faulty.
VOLTMETER!!!!!!
Good luck.