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Hello, I'm Chris.I will do my best to answer your question fast and accurate using the info you have provided. Thanks for visiting Just Answer.
This system requires alot of diagnostic steps. Most shops just have a few known good parts they can put on the vehicle for testing purposes to defeat the long diagnostics needed to identify the origin of concern. For this issue it can be the switch or shift relays or shift motor or module. You can see and perform all of the diagnostics by downloading them here.
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I appreciate your answer and the information you provided. I'm sure this will be very helpful, however, there are some terms and devices that I do not know the location or the meaning. For example, the test calls for measuring voltage at circuit 1052 on CJB C243-11. I assume CJB means circuit juntion box, but where is C243? Also, on page two the test calls for monitoring the GEM pids. What the heck is a GEM and the designation abbreviations it requests to be monitored such as ING_S, ING_R etc. etc.?
Central junction box is the interior fuse panel in front of your left knee and the connectors are on the back of it.
The Generic electronic module is the module which controls the 4x4 and is mounted to the back of the CJB.
To monitor pids you must use a scan tool and bring up items to check including ignition switch position
When I turn the switch on I've been noticing a clicking noise somewhere in the dash. The adventurer that I am I took the dash apart and found out that it is the Transfer Case Module. Think this might be the culprit?
The GEM is mounted ]on the back of the CJB.
When you see this image below it means to do the testing while the connector is unplugged.
Thanks, XXXXX XXXXX're really helping a lot. Now, I'm at the point where I need to get into the GEM connector. I tried taking out the bolts and screws around the fuse box hoping it would simply drop down and allow me access, however, it's never that easy. Can you help me again?
While waiting for your answer I got a mirrow to see if I could look behind the CJB and see the GEM. It looks like it might be the box behind the CJB mounted to the firewall, although, if it is, the circuit I need to check is on neither of the conncectors plugged into this particular box. Can you help clarify?
I work a normal job during the day and can only respond during the evening after work.
All the fuse panel mounting nuts and bolts are on the front. Then there are 2 large bulk head connectors to unscrew and dismount from the rear of the fuse panel to allow wiggling it out for removal. Once out you will see the GEM screwed and mounted to the back of the CJB looking like one large assembly.
Ouch, that kind of makes it a little rough on me. I guess if I'm going to solve this problem using this service I need to spend some evenings in the garage.
By the way, cute little guy you're holding there in your pic. Is he the real expert?
Anyway, back to business. Does the fuse box (CJB) definitely have to be removed to access the GEM? It didn't look to me like there was enough room in the fuse box block for the fuses, contact points and another item (GEM). If it's in there, it will certainly be interesting to see how they cram all that into that same small space.
He wants to be the expert, but not just yet. He is going to leave that up to me, however I wish they would change our title to TECH since no one is a true expert.
DOWNLOAD this file and click on the image below as well.
Well, I finally got that bad boy fuse box out. It really wasn't that hard once I quit babying it. And I think getting it out helped me find the location of the problem.
In the beginning, when I was searching for the clicking relay, I also found a mouse nest on top of the dash near the relay. I do not have continuity between the GEM circuit 780 and the mode switch connector (Test A13). However, the 4x4 lights sometime illuminate in the dash and I think the transfer case trys to (at least) partially engage because the truck will at times not move when shifted into drive even though the speedometer is active showing the trans is turning.
I traced the GEM 780 wire and the mode switch wire and they both go behind the dash panel. Since I definitely have a problem in this circuit that needs repair and it would appear others, I believe mice may have chewed into the wiring behind the dash panel. Is it possible to remove this panel to access the wiring? How hard is it? And, do you have any info on removing it?
I've already removed the 4X4 switch panel and the switch for testing. I wish that would have been enough to find and repair the problem. However, it appears to me that the complete dash or dash cover will have to come out to access the wiring harness that includes this circuit. I feel that if I can open up the dash and trace the 780 circuit, not only will I be able to repair the 780, but will also locate the source of the other issues that seem to plague this system.
I feel that the only way to effectively analyze the problem in this circuit is to gain access to the harness that appears to be enclosed in or in back of the dash. Although, I'm certainly not an expert, so if you have another idea, please enlighten me. Otherwise, please enlighten me with a diagram or other information to help me get this dash out easily, and in one piece. Thanks
Thanks Chris for the dashboard download.
I have always believed in the old sayings "Two heads are better than one" and "Where no counsel is, the people fall: but in the multitude of counsellors there is safety. Also, I sense that you are a very wise person and have good problem solving skills, so before I start this arduous task of taking this dashboard out, do you any ideas that might be an easier way to solve this problem?
Working on the 99 ford again today and I have a dilemma that I hope you can help me work out. On the test procedure you offered for me to download, test A13 indicates there should be continuity between circuit 780 and the 4X4 switch connector. I'm reading infinity on this test which leads me to believe it's a open wire, however, the test A15 shows there should be voltage in this circuit. How could there possibly be voltage when it's disconnected from the GEM. A schematic that I got from Alldata shows the it's a straight shot for the GEM connector to the 4X4 switch. I'm also having the same results with test A16 and A18. What am I not seeing?
On test A13 make sure your multimeter is actually touching the pins, you may need to push a straight pin into the GEM connector to be able to touch the pin since the hole is to small to get a multimeter probe into.
On test A15 there should be no voltage, your testing for a short to power here. meaning this pin has power from a wire short some where in this circuit.
I did need to use a straight pin. I can't believe those connectors are that small.
Anyhow, help me understand the difference in the look of the transfer case connectors shown in test A36 and A37. I thought maybe one was the case side and one was the control side, but the pin configuration doesn't match that theory.
There is only one connector for the transfer case mounted shift motor and the other connector its referring to is the relays mounted.
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Agreed, but there are definitely two different views. Schematics are usually pretty acurate with their pictures. I just didn't want to misunderstand and mischeck on this procedure.
I don't have an NGS and really don't feel like spending $1000 just to check this vehicle, so some of the tests are not possible to do and some I've merely thought about what they are trying to prove and tested another way. Regardless, this thing is starting to drive me nuts. I've resorted to just trying to figure out the schematic diagrams and test that way. An item of concern at this time is I have power on circuit 704 at the shift relay module but nothing on circuit 777 and 778. It would appear that circuits 781 and 782 are not making. However, if I jump 704 directly to 777 or 778 nothing happens at the transfer case.....Arrrrrggggg!!
Any idea what triggers circuit 781 and 782 in the GEM.
Well Chris, as I suspected, circuit 781 and 782 are what's keeping the T-case motor from running. I can run it manually by grounding those circuits. I get the impression that you don't know what causes those circuits to ground. That's ok, 'cause like you said, there really are NO experts. However, if it's just that I've used up my nickel, then I rather pay you another $18 to keep the same guy that knows what we've done so far. Please let me know one way or another.
The GEM module grounds these 2 circuits, I sent this diagram earlier and I assumed you saw that, but I will point it out this time.
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I did see it, but my question is, are there any inputs that causes this circuit in the GEM to ground or not ground? It is obviously a "Switched" ground. What causes the switching action? To me, knowing this is key to determining if the problem is the GEM itself or an input to the GEM.
The switch on the dash tells the GEM module you want 4x4 then the GEM switches the grounds on and off.