Ok I posted on here and a few of you said to test some thing before posting again so here is what i got and where I need input. This is on my 97 F150 XLT 4x4 with electronic shift.

My 4x4 High will no engage with selecting 4H with the electronic shifter. 2H and 4L will. I replaced the switch removed the TC motor to see if it actually is moving it. It does not. When you select 4H the relays clicks under the oval by the passenger side.

things I did:
-replaced the stock TC motor and it did the same so I took that back and put the stocker back on. I had the motor off the TC to see if it spins the rod that actually moves it in to the selected position.
-replaced the electronic switch, still doing the same thing.

-bench tested the switch to make sure it's not bad either. I get the specified ohm resistance reading for 2H,4H,4L as I was told to check.

-I moved the relays around under the oval to determine witch one is for the electronic shift, but they all made the clicking sound. It just clicks click clicks clicks when you select 4H. Light does not come on and the clicking just keeps going till you select out of 4H.


questions I have:
-Does the GEM see anything after the switch has it's selection made or does it go the Relay and then to the TC motor?
-how do I test he signal after it leaves the switch?
-hint on how I can check at the relay to see if the GEM is sending the right amount of voltage.
-what pins can I check on the wiring harnes on the TC motor to see if there is anything going to the TC motor. I would assume no voltage since it's not moving when a selection is made.
-it was mentioned there was a relay behind the dash, guidance on how to get to it the easiest would be appreciated too.


thanks for any help. I'm really hoping to get this fixed this week since the snow is coming.

Thanks,

 

tonight I looked at the vacume lines and noticed something strange and this might be my cause. There are 2 vacume hoses going from the front end light blue and red or orange that go behind the battery. There is also a black rubber hose (larger) that is plugged into the front end that runs along the vacume hoses....does that black hose lead to somewhere or is that just a breather hose? I was looking at it and it seemed to be cut, again that is if it's not a breather hose. Just seemed odd.

 

From the 97 F150 Electrical manual:

The 4wd mode switch is a set of resistors that provides input to the GEM. Depending on the switch position the GEM reads the resistance (3.9k, 1.1k, or 360 ohms) You can test the signal after it leaves the switch by measuring resistance between pins 2 and 3 of the mode switch connector.

The GEM sends a ground signal out on pin 14 of connector C241 (Orange wire) to the 4wd relay which is located under the removable oval tray on top of the passenger's dash. The relay should have 12vdc on the W/LB and DG/LG wire, but only have 12vdc on the BR wire when 4wd is selected. This wire is what energizes the Magnetic clutch coil in the transfer case to give you 4wd.

The GEM also sends ground signals (Only one at a time on C241 pin 16 BR/W & 17 O/LB) to the transfer case shift relays which are located above (and to the left of) the radio. You can only access them by removing the main dash bezel that surrounds the instrument cluster.

During all this switching madness, the GEM is constantly monitoring the TC motor position by way of 4 switches in the transfer case. The large Orange and large Yellow wire going to the TC motor only have 12vdc (ONE AT A TIME) to move from High to Low range and back. This is all the TC motor does...move from Hi to Low and back.(works just like a reversing polarity power window motor)

Here's what's interesting about your situation. You say you have 2 High and 4 Low which indicates that all the relays are working and TC motor is functioning. If you get 4Low then that means the motor is moving to low range and the magnetic clutch coil is engaging 4wd. If you go back to 2high, then the TC motor is moving back to high range and Magnetic clutch coil is disengaging 4wd.

I would first check and make sure that you have a ground signal on the GEM Connector C241 pin 7 (Red wire) when you select 4high. This ground signal goes to the 4x4 hub solenoid. You say you have 4low, so this wire MUST be getting a ground signal when 4low is selected (You cannot have 4wd otherwise). If it is grounded in 4low and not in 4hi, and you've verified your mode switch and its wiring, then you have a problem with your GEM (it's either not recognizing the mode switch input, or not processing it correctly).

FUN STUFF!!

 

thanks for the input...I'll see if I can test what you recommended. I admit I'm not realy sure where those pins are you are talking about. Are you talking directly at the GEM or at the relay at the oval or by the hub selenoids? OH and I would'nt call this interesting

I've tried a lot and it's really getting to me. I counted the GEM out because it does engage 2H and 4L, just not 4H....and since I can hear the relays clicking clicking clicking I thought it was sending the signal.

Someone mentioned a "oil switch" by the TC motor, something about it sends signal back to the GEM, just a ground singnal and that switch can go bad. I guess you can check that by putting a ground to the switch and seeing if you get it to work. I got that off of another forum. Would that cause my issues or no since 4L and 2H work?

Thanks again.......if you have time and can get into more detail on how to check those pins and ground please feel free because it will deff. help.

Happy Holiday's everyone!

 

You are rolling while you try to go into 4H, right?

 

No...I'm trying to engage it while sitting in D or park.

Should technically still engage right or are you saying 4H will only kick on at a certain speed or as the wheels are moving?

I'm almost 100% sure it should be switchable sitting there.

 

I have a 04 f150 fx4, I having the same problem, it works fine in 4w Low but it wont engage in 4w high, the light flashes but doesnt come on. I hear it trying to come on but it wont.

 

u mean you can hear the relay clicking in the dash correct and it just clicks or what? You mention you light flashes, does it continuously flash or only on start up? I'm a bit confused what you are saying.

When I select 4H, I get no light just the sound of the relay clicking under the oval on the passenger side dash.

Supposedly there are some relay's behind the radio or to the side of them. I have yet to be able to reach or locate them.

There is also a switch (ground) on the transfer case that sends a signal to the GEM, I'm still waiting to hear back if our Electronic Shift versions have this switch. I got info from some other board where folks were having our issue but they had the 4x4 with the manual shifter not Electric....so we might not have that switch they were talking about. I'll post back if I find out what was wrong with mine. They called it a "oil switch and it went bad and. The verfified by putting a jumper wire into the harness and it grounds the wires. The 4x4 light came on and so did the 4x4 high then. I guess this switch is a ground and sends signal to the gem which activates the 4x4H.

 

A,
Sorry, I kinda forgot about your emails...been kinda busy around here. I see you're still fighting your xfercase.
There isn't a separate switch like the manual shift cases have, the ESOF model uses the multi-wire switch on the back of the shift motor to provide the shift feedback info. Once the GEM gets the signal that the transfer case is shifted, then the GEM sends the signal to the vacuum solenoids to engage the front diff.

I was inside the dash of my 97 a couple weeks ago working on the radio wiring and I still couldn't find the 4x4 relays. I know they're down there someplace but I can't find em either.

Have you tried checking the ohms from the selector switch down at the GEM? If 4lo is still working I have a sneaking hunch your problem lies in the GEM.

Did you ever get your power window problem taken care of? That's another bug that keeps pointing towards a faulty GEM.

Mike

 

Mike,

The windows are working again. I got another set of switches for the dirve side installed them and now they seem to work. At first they didn't, but now they do. Kind of weird I guess. Could be GEM related I guess.

Just so weird to hear the relays clicking for 4H but nothing going on. I didn't check the ohm reading on the transfer case motor because I'm not sure which pins to use or pin that is. There are 7 and if you have use 2 together it can go on forever. I'll see if I can do that if someone can can tell me witch wire color pin to use for the different positions.

Thanks again.

 

Not the resistance of the motor. I'm thinking the resistance of the mode-select switch except at the GEM instead of at the switch itself.
Might be a funky wire from the switch to the GEM...enough extra resistance from a crappy connection or pinched wire to affect the resistance reading of the switch at the GEM itself. In 4H, it should be roughly 1000ohms plus/minus 50. you can also check that wire from theswitch to the GEM by ohming the wire itself. I think it's pin 3 on the switch and pin 8 on the upper row of the GEM connector...the pin locations on the plug are shown in that pin-point test PDF I sent. Check Section B14.

I can't find my pinout diagram for the feedback switch assembly that's mounted on the transfer case motor...if I can find it I'll send it your way.
It's possible that the contact that is supposed to be "made" for the 4H position is keeping the motor from actually shifting the case that far. since the problems is the same with another shift motor then I'd maybe think it's a bad wire from the shift motor feedback switch to the GEM instead of the feedback switch itself. 4H should be contact "C" on that switch if I remember right...I might be mistaken though.

 

Mike,

If the wire into the transfer case (the single wire that charges up the coil inside the transfer case) is not hooked up, but the car is in park, will it cause my issues? Whe I bought the new TCM, i didn't hook up that wire because the new motor needed to have that wire attached. It didn't come with that pin in place, I installed the new motor but same thing it didn't move to 4H. does the GEM require that wire as a signal to engage 4H?

 

I sent the electrical schematics your way this morning. sounds like you might have some crossed up wiring on that TCM connector. Connector C200 in the schematic.

Pin 16, the brown clutch wire, needs to be in that location. The motor itself should be on pins 14 (orange) & 15 (yellow).

Here's the other wires and what pin location they should be in:

TCM contact plate assembly:
1-white
5-pink/violet
9-brown/white
10-violet/white
13-orange/white

 

so I found the relay module....you have to remove or pry up on the front dash area.

When I select 4L I can feel the module clicking, when I select 4H though nothing.

Is there a way to test the module/relay or would that indicate it's bad. I guess I'm not sure if the signal goes from the module/relay to the RPO box or if the singnal goes from the RPO box to the module/relay. Also finding that part sucks. I tried searching on google and got nothing.

This is the number written on it.
F75B-14B194-BB

When I select 4L i can feel it clicking inside the module relay, but when selecting 4H nothing, just the relay in the RPO box clicks clicks clicks.

Thoughts?

Any way I can check if the relay module is working correctly? Bench testing it or something? There are a lot of pins on that module realy.


Also, Mike
I admit I'm horrible at lookin at wiring diagrams etc. I'm more of a mechanical person than electricla. But, not having the brown wire for the coil in the TC hooked up should not keep the motor from selecting 4H correct.

 

Yeah, That brown TCC wire being unhooked shouldn't be a problem as long as you're not doing any moving shifts.
I'm still kinda worried about you saying that it wouldn't fit in the connector because the one of wires for the shift motor are occupying it's spot on the connector though. doesn't really make sense to me though since your 4L shifts seem to work properly. Makes me wonder if there are other wires in the wrong place (like the 5 wires for the shift motor position switch on the shift motor)...this might make the GEM think it's in a wrong range and be preventing the 2H-4H shift from happening.

On that shift relay module, there are two relays inside the module...one for clockwise shift motor rotation and one for counter-clockwise rotation. If they're working for the 4L shifts then they should be fine.
-For a high-to-low shift (like 2H-->4H, 2H-->4L, 4H-->4L) the orange/light-brown wire on pin 9 of the module should get grounded by a relay inside the GEM and flip the H2L relay contact to provide +12v on pin 10 of the module (orange wire). The yellow wire on pin 7 should be at ground during this shift.
-For a low-to-high shift, the brown/white wire on pin 8 of the module should be grounded by a contact inside the GEM and trigger the other relay to provide +12v to pin 7 and pin 10 should be grounded.

Since you've already tried swapping in another shift mode select switch with no change and your 2H-->4L shift & back is okay...the problem sounds to me like it's back at the GEM or the shift mode select switch to GEM wiring. Either the GEM isn't getting the right signal from the shift switch for 4H or it's not processing it properly inside the GEM to trigger the contacts inside the GEM that drive the relay module.