I'm new here & this is my 1st post to any forums so new using forums in general but I've got a lot of useful info from reading this forum. I really hope I didn't overlook my question already answered somewhere else.

I have a 02 Ford Supercrew Lariat 4x4 that I bought new that now only has 80k miles. It's never been off road, just ran a few miles in 4wd every 6 months in sand as someone at Ford told me to do. After hurricane Harvey I needed the 4wd bad but it wouldn't go into 4H or 4L. I started by replacing the 2 solenoids on the firewall by the battery with no luck. It has a 1-off vacuum hose setup that has 2 sections that connect right under the battery going to the front differential. I read were people had trouble with battery acid leaking on this hose causing damage so after a lot of searching I was lucky to find a set of the 2 OEM hoses. After getting the truck on the lift I found no leaks in these lines so I held off on putting them on. I checked the vacuum box behind the battery for cracks or leaks & that was good. On the vacuum hoses you can put vacuum on each hose & watch the vacuum solenoid move the little arm on the front differential back & forth but honestly I don't know how much that arm should move when locking/unlocking the hubs.
The dash 4wd lites come on when the key is 1st turned on & when you put it in 4H you can hear the relays behind the dash clicking but it doesn't go into 4wd. I think it might be the shift motor & was looking to see if anyone had a wiring schematic that shows which wires should make the motor move or if someone could just tell me what color wires do what & which need voltage applied for a bench test. I think it has 7 wires that go to the motor which I don't understand when your just going from 4H to 4L & back again. I know a grey or brown wire goes through that harness but its for the speedometer & has nothing to do with the motor moving. The PCM might use that info to allow the motor to move when the truck is moving but I think that shouldn't effect a bench test. I used to buy a new Ford 4wd every 2 years & some of those have been hell with the shift-on-the-fly & I never had a problem.

I'm an electrician & bench testing the motor before just throwing money at it should be easy if someone has a wiring diagram or can tell me what color wires do what or what wires to put voltage on to test motor function. Also,when I pull the motor/plate assembly the trans case, will I get any nasty surprises like springs or fluid coming out? I've gone through this system as best as I could & I'm drawing a blank & don't want to buy a shift motor if not needed. Any comments or advice would be much appreciated. Be it about my truck or if I've used this forum wrong.

 

You need to know how the system works first.
101./
Dash switch to 4H requests the Gem module to run the transfer case motor to it's first position engaging the 4w drive line.
This action operates one firewall solenoid that routes engine vacuum to pull in the front axle lock sleeve.
These actions result in the GEM lighting the dash 4H light.
.
If you hear relay clicking, that is repeated attempts to operate the case motor.
The case motor turns a shaft to engage 4w drive train. There is a circuit board in with movable contacts that does the firewall and other signals.
Dash switch to 4L runs the case motor one more position and engages the gear reduction drive and signals the PCM to change shift rpm skedual.
Dash switch off reverses these functions.
.
Trouble shooting: If you hear the case motor relay clicking, the Gem requests would be good and tells you the sequence never got to the front axle functions.
Remove the case motor and still plugged up try 4H to see if the motor runs and go from their. It may be froze or circuit board has a problem..
The dash relay applies power to the case motor and reverses polarity to run it back.
What does it do? Page 212 in your owner manual, fuse location 104 a 30 amp fuse.
Note; the PCM has no control of 4wd. It only responds to 4L when shift sked needs to be changed so shifting is done for the reduction in gearing.
Good luck.

 

Sorry about time getting back with you but I work shift work.

Everything you said sounds correct and this is what I've done so far.
1. I took connectors off the 2 solenoids on the firewall. With the key on but the truck not running, I put my meter on the right 2WD (looking at the motor) solenoid and the meter lit up or showed power in 2WD. I next moved my meter over to the left 4WD solenoid connector and moved switch to 4H and the meter lit up and showed power. With the switch still in 4H I moved my meter back to the unlock or 2WD solenoid and no power was shown there.
2. I next put the electrical connectors back on each solenoid and started the truck with switch in 2H and removed the bottom of the double vacuum hose on the 2WD solenoid and vacuum was coming from the bottom of the solenoid. I did the same with the 4WD solenoid (next to battery) and then turned switch to 4H and vacuum stopped coming from the 2WD solenoid and started coming from the bottom of the 4WD solenoid, all correct.
3. I put all the vacuum lines back on and checked the vacuum tank behind battery to make sure there were no leaks or cracks and it was good.
4. I put the truck on a lift to get to the actuator on the front diff. I 1st left it in 2WD and made sure I had vacuum to actuator which I did. I pulled the 2 hoses off and took the one with vacuum and moved it from the top of the actuator and then to the bottom of actuator. This caused the bar to move back and forth but I have no idea how far it should move each way, just that it did move a little back and forth as I moved my source vacuum hose around.
5. I attached the double ended vacuum hose back to the actuator and with the motor running I had a guy in the truck working the switch from 2WD to 4WD. At this point I was just trying to check everything I could, not try to get it into 4WD, just making sure parts were working. Again the bar going from the actuator to the inside of the diff moved back and forth but I still don't know if it moved the correct distance. I've read that these actuators could become weak or just go out all together and from everything I've priced, that little actuator cost the most, even more than a transfer case motor. So it might not be moving the correct distance, I've not found anything in my research that tells how much that rod should move each way.
6. During all of this I was standing under the truck and being under the truck or setting inside, you know when the transfer case goes into 4WD. You can hear it under the truck and feel it in your bones setting inside the truck. Driving down the road it didn't seem to make as much noise going into 4WD vs. setting still but that might just be because the truck was moving and I didn't hear it.
In my owners manual it says it's safe to engage the 4WD/4H at speeds up to 60 MPH, but I've never done this. I always thought that was a lot of rotating mass to engage 4WD at that speed. I think the fastest I ever went was about 35 MPH when I engaged the system but only a couple of times. I've never had the truck off road and living in South East TX we don't get much in the way of harsh winters but in the 16 years I've had the truck, we have had some bad icing a few times and I did use the 4WD. We had a little out of the way swimming hole I went to maybe 5x's since buying the truck new and it had a hill of nothing but deep sand you had to go down to get to the swimming hole. You could make it down the hill in 2WD but you had to use 4WD to get back up. Even now with only 82k miles on the truck I've keep replacing the OEM Goodyear Wrangler LT truck tires with the same since I never had plans to use a $40,000 truck off road.
5. Now the last thing that happened when I had the truck on the lift was after several times of cycling the switch from 2WD to 4WD without anything from the transfer case, the relays behind the dash just stopped clicking altogether. Now when you turn the switch back and forth, you get nothing. No relays clicking, want switch to 4WD solenoid on firewall, nothing of any kind. I looked in my owners manual for fuses and it has one in the cab (#104/30A mini) that says "4x4 Shift Motor and Clutch". Then one under the hood (#23/10A, the large square type with element window on the top) and this fuse also includes the "Turn/Hazard, Flasher, 4x4 Solenoids, 4x4 Relays, Overhead Console, 4 Wheel Anti-Lock Break System (4WABS) Module, EC Mirror" and everything listed with this still works except the 4x4 system and I never had any type of warning lights come on, on the dash. Now I don't want to offend anyone but I'm a self employed electrician and I use high dollar Fluke meters to check these fuses. I have friends that will only look at a fuse and sometimes they look good when in fact it's bad and both fuses checked out good. With the shift motor I figured it would have some type of relay under the hood or in fuse box in the cab. I might be wrong, the relay wherever it is behind the instrument display might be the only one/ones.

I could hear it clicking behind the dash before it stopped altogether but I've never been able to put my finger on where it's at. I had a 97 F-150 which wasn't a 4WD and now the 02 I'm having the problem with which are close to the same body style/ type and I've gone to Helminc with both trucks and bought the F-150 Workshop DVD but I've never figured out how to get PN's or figure out the troubleshooting. I've figured out to remove and install parts using these manuals but each part has a number beside it but it's not even close to the PN that's on the box if replacing with OEM and they say you can get any PN with this manual. So... about 6 months before hurricane Harvey which was Sept. 2017 was the last time I put it in 4WD and it took several try's for it to engage, before that no problems. When Harvey hit I really need the 4WD and it let me down and I've been pulling my hair out ever since. The truck was never under water nor was water even close to the transfer case. I went to help a friend that lived down a long wet sandy road and before turning down his road I tried to put it 4WD and when I knew it wasn't going into 4H or 4L I turned around and left. I've never had a check engine light, a flashing 4WD light that someone told me might happen when there's problems with the system and I don't know if the 4WD system stores error codes without me knowing. No one has told me this but I've wondered if a bad 4x4 motor would shut the entire system down, including the relays clicking behind the dash.

I'm sorry I put so much info here but wanted anyone that might be able to help to know everything I've done. The reply to my post it says "There is a circuit board in with movable contacts that does the firewall and other signals." There is a big plate in front the transfer case motor that has several wires going into it and I wondered if there are contacts on the other side of this plate and if I take the motor/plate off to check the motor, is transmission fluid going to come out all over me or does the case need to be drained before trying this. Also with all the attempts of me trying to troubleshoot the system, will this put the PCM in a self protect mode causing the clicking relays behind the dash to stop working? I'm grabbing at straws here and it's hard for me to understand how a garage keep truck, rarely used 4WD just quits. Any ideas would be MUCH VERY APPRECIATED NO MATTER HOW MUCH INFO IS GIVEN!!!

 

All the lift test seem to be correct at that point.
The case motor is all a dry area, no fluid.
It operates a shaft to engage the case into the drive train.
Remove the motor, inspect the circuit board for plane and contact issues.
Note: The system cannot indicate anything about the front Actuator because there is no electrical or technical monitor at that point.
The dash indicators are operated by the GEM after get8ng signal back from the case motor circuit board position changes.
The PCM has no control over any of these operations.
The only association to the PCM is a bus pair to tell the PCM to change shift schedule.
If this does not happen, the shift rpm will go very high before upshifts. You would not like that.

 

I kind of figured that was the case on the front Actuator. As I started working from the firewall down I noticed there was no wires past the solenoids going down towards the Actuator. I just don't understand how something the uses vacuum just to pull & push a rod was almost $300 & the transfer case motor I can pick up for around $100. Just hope the motor comes with the plate that has the switches & circuit boards included. I had no idea those things would be behind that plate so I didn't look to see what all came with motor.
2 questions you might be able to answer since you sound like you know a good bit about this 4WD system.

1. The rod on the Actuator, do you have any specs on how much that should move either way?

2. You mentioned behind the transfer case motor is a dry space with circuit boards and limit switches or switches. Does this plate have a gasket on it to keep it dry? If it does I might see how this might've got screwed up if that's the case. A premature failure of a gasket to a dry area could be a reason for problems. As I stated before the truck has never been off road or even driven in high water but... There is a touch-less car wash I use in town when I don't have time for it's weekly bath & it has a high pressure under carriage wash. if I had a failed gasket on the transfer case motor water could've got in this dry area & damaged the circuit boards/switches or even by just driving it in the rain. Again, only 80,250 miles as of today but I've probably taken the truck through that car wash at least once every 3 months for the past 16 years. That makes me sick thinking I was doing damage to my truck by simply going through a car wash, if that turns out to be the problem which seems more and more likely.

You've opened my eyes now & I bet I'm going to find a mess when I pull the trans case motor off. You've been a big help & again I want to say I sorry for putting some much info in my last couple of post but I wanted anyone that might read them to understand what steps I'd taken thus far so we wouldn't be going back over covered ground again and again.. I'm truly grateful to you and I 100% appreciate all the help you've given me to date!!!

I wish I had more knowledge about Ford trucks so I could try and help others. I'm 51 now and starting after I graduated school I bought a new Ford truck every year and I would put about 60k on them in that year. Back then I did most repairs myself but as time when on you just about had to be schooled to do your own work. I didn't think there would be this much to just a 4WD system but I was really wrong. Still doesn't feel right getting help with my problem and not be able to help someone else out. I'll keep reading and maybe I'll run into someone needing help changing out wiper blades or putting in aftermarket stereo equipment since I know a good bit about those subjects. LOL

 

One more thing I just read looking at transfer case motors. One had a PDF installation guide and the very last thing it told you to do was:

 

You are beginning to trip over yourself!
Transmission codes are unique to only the transmission Electrical operation proper. The PCM checks to electrical grounds, opens and crosses, stuck solenoids, slow operations etc. in the shift solenoids, converter lock etc.
Nothing in 4wd operation.
No 4wd or the case motor operation.
Again 4wd is controlled solely by the GEM and it's related hardware.
THE only feed to the PCM is a CHANGE signal for shift sked in 4L. I explained why!
DO NOT read about FWD 2004 and later because they are not the same system as what you have..

 

I agree with your last post 100%. I've been letting what others have told me to mix with your advice when you seem to know this system forward and backwards. When you said to check the "circuit board" inside motor assembly it made me think about the bad advice I'd been given about check engine lights and error codes. I now see that one thing has nothing to do with the other. I will pull the case motor and if something looks wrong I'll leave what I found here and hope your still around for advice. The only reason for not just pulling the transfer case motor was the fact that I had no idea if I would be opening a can of worms or not but you've made that clear, it's not.

AGAIN, I appreciate everything you've helped me with and when the motor comes off, I really hope you'll still around if I have a question.

 

Bluegrass 7,
I hope you get this update about my 4wd system. After a month in ICU and time recovering I installed the transfer case motor and the system worked perfect just as you said. Now I just want to thank you for all your help and advice. I worried about everything that didn't matter so I just installed the motor and everything fell into place.

Thanks Again,

 

Great to hear you doing well and it all worked out.
Good luck.

 

I'm doing about as good as anyone that spent almost 2 months in the ICU can. LOL

No one but you every replied to this thread and going back reading my post I could see each one I tried to drift to something else but you keep pushing me back to what turned out to be the problem, the case motor. One of your last replies kind of reminded of my dad for it sounded like you wanted to just hit me in the head with a hammer and tell me to just install the motor and your problems would be over. I had done so much research on this 4wd system and advice I'd seen others give made me think springs, screws and switches would come falling out once I removed the motor. After getting over this fear I just did what you said and BINGO, it worked. Take that back, the 1st time I tried it I got none of the clicking relays or even the dash light. I killed the truck as I was thinking about getting some gas and matches but I decided I would try it once more after driving it around the block but as soon as I started the truck to do this and before I even moved the truck the relays started clicking and I felt the truck go into 4wd this time. After the 1st try with no luck I killed the truck leaving the switch in the 4H position. Just as soon as I started it the 2nd time it went right into 4H then 4L and back to 2wd again. Don't know why it didn't work the 1st time but just minutes later on my 2nd try it worked like it should.

Most of my trucks have been new 4wd Fords and all got used hard. I would buy/order like the XL package which didn't have carpet and then add most of the power options where I had a XLT without carpet. This Supercrew Lariat Fx4 I couldn't bring myself to take it off road being a garage queen and that brings up one last thing I'd like you impute on. After hurricane Harvey dumped 52" of water this was the 1st time I called for the 4wd in over 2 years and it didn't work. I have no idea when it quit working but I'd guess it had been at least 2 years since I used it and then I wanted my mechanic to let a little oil out of the front and rear differentials just to see what shape it was in. He told me that I needed to drive it about 20 minutes in 4wd because the front end was so cold the oil wouldn't even come out. We have a big river that runs in, out, through and around our town and I knew you could drive almost a mile along this river were it was just deep white sand roads that came out at several sand bars and that's how I warmed it up for the guy and that's the last time I remember putting in 4wd. What's your opinion on how often you should use your 4wd? I've been told I needed to do it a couple times a year going about 10 miles each time. Others say you need to drive it in 4wd ever month for about 10 miles. I've read my owners guide looking for info on this and it says nothing about it so do you have anything you'd like to add on that??? You've been a big help so far, I figured you might know something about this...

 

What gets exercised is the transfer case motor/ electric sync operation, engaging the case gear train, the firewall solenoids and front actuator and power to the front drive shaft.
No need for 10 miles run.
Just check it all works well before you need it.
The front running gear turns all the time, in or out of 4wd.
Good luck.

 

Everything is working perfect thanks to your advice. Can't tell you how much that advice was appreciated!!!





Eric

 

I've been having similar issues with my 2002 f-150. When the 4x4 switch is turned to 4x4 the dash indicator light don't come on and 4x4 doesn't engage but I hear clicking in dash. I have power to my constant hots on both selonoid switches but no switch ground to my 4x4 sylonoid when switch is in 4x4 position, although I do have both a switch ground and constant hot to the 2 wheel drive sylonoid. I'm getting good vaccume to both solenoids but no vaccume from 4x4 solenoid to actuator because the switch ground isn't engaging allowing 4x4 solenoid to activate

Any help would be very much appreciated

 

See above in your quote,
.
Dash switch causes case motor to rotate...…………………..
.
This action operates the firewall solenoids.
.
From your description, this is not happening. The motor is not moving or the contacts on the circuit board are faulty that passes ground to the firewall relay.
This is what brings the dash light on. The motor has to operate.
Good luck.