How to Troubleshoot and Fix F150 4X4 1997-2003
 

I am posting this because it took me AGES to find this information and peice it together from many sources all over the internet. From a girl who knew NOTHING about these systems a few weeks ago - here is a quick and easy guide to troubleshooting your 4X4 problems -- mostly for Manual shift on the floor (MSOF) systems or what goes on mechanically after you press the button on the electronic systems. All you need for these tests is a friend, and a socket set.

The 4X4 works with two systems - the shifter on the floor manually engages the transfer case. It also causes a relay to ground one of two solenoids that cause vacuum lines to activate an actuator which engages the front differential. If either of these do not work, your 4X4 won't work.

In my case, ad most that I have read, the 4X4 simply does not engage and the dash light either always goes on or does not go on.

1. Rule out transfer case problems: This is easy - get someone to put your truck in 4X4 and roll forward while you peek underneath from the side. If the front drive shaft is turning, your transfer case is fine and engaged.

2. Check the fuse! #23 by the hood lever and parking brake under the front dash.

3. Check the functioning of the solenoids: this is easy as well. The solenoids are located in the passenger side of the engine compartment directly behind the battery on the firewall.

From what I have read, a good indication of a problem here is the absence of the dash light. You can get fancy and test them electrically (they should each have 12V power all of the time) but the easiest way is to put your fingers on the plastic caps and feel and listen for a click as someone shifts your truck in and out of 4X4. If they click - they are working! If not, this is likely your problem. It is a common problem apparently for these years of trucks to get water in the solenoids which then freezes and cracks them.
Here is some good info and part numbers if this is your problem
"The right solenoid (E8AE-9H465-AA) controls the vacuum to the return side of axle engagement diaphram. The left solenoid (E8AE-9H465-BA) controls the vacuum to the activation side of the axle engagement diaphram. Ford has been having chronic problems with water entry into these solenoids, corroding them from the inside and seizing them,as you've seen!<O:p></O:p>
They've been redesigned and those old part numbers (E8AE-9H465-AA/BA) have been superseded.

The latest designs are listed as:
Disengage solenoid 6L3Z-9H465-A (identified by electrical connector rib at 9:00 position)
Engage solenoid 6L3Z-9H465-B (connector rib at 6:00 position).


3. Check your vacuum lines: This is a little tricky to do becuase they wind their way from the solenoids all the way to the 4WD actuator on the front axle. One hose leaves from each solenoid at the front (close side to the battery) and one is pink and the other is blue(greenish if older). Follow the lines down as best as you can, checking for spots with wear or rubbing. Also make note if they seem old and brittle as there could be a crack you don't see. Mine were rubbing a bit on the passengers side wheel well so check there. Now crawl under the truck and in the centre on the axle is the actuator diaphragm. It is under a cover that is easily removed with a socket and the two hoses are attached to it. Pull the hoses off and while the truck is on, and someone shifts it in and out, put a finger over the end of each hose. The vacuum should alternate hoses when shifted and the pressure should be equal although it is surprisingly not a strong pull. If your hoses look good and suck like I said, they should be all good (this also confirms that your solenoids, and vacuum reservoir are working as well.)

4. Vacuum actuator function: This is easy to check. Crawl under your truck, take off the cover for the actuator and watch as your friend shifts from 4X4 and back. When the truck is shifted to 4X4, the shaft should slide into the diaphragm, moving the lever it is connected to to the passenger side direction. When shifted back to 2 wheel, the shaft should slide out of the diaphragm towards the drivers side. The movement is about 2 inches total and happens smoothly.
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If this works, then you may want to check to see if the shift fork (the lever that the actuator moves) is not bent or broken, or the pin that holds it in place is not sheared. It this all good, then maybe your front differential needs help?

If the diaphragm moves stiff and short, it is one of two problems: there is a tear in the diaphragm or the shaft has corroded and is stiff and needs lube. To check if the diaphragm is just stiff, assist the truck by pushing the shaft in an out by hand. This should engage and disengage the 4X4. When I did this, I engaged the 4X by pushing the shaft in but it was very stiff and hand to pull it out again with leverage from a screwdriver. Mine was just stiff and needed lubrication - which worked! If you can move it freely by hand, I would say there is a tear in the diaphragm and you probably need a new one. Try ebay -- they are $100 where at Ford they are $460!! Part number is F65Z-3G360-BA

Hopefully this helps and will guide some other less than mechanical people towards fixing a problem for cheap or free!

Good info :-X22

97 F150 4X4 Quit Working!
 

Great Info!!! Hope I can use it and find another problem thinking it might be something in my front diff, but I am going to check your ideas out and hope for the best. The info on the drive-axle turning might just have saved me from tearing my differential down!! Thanks alot!!!! And for ANYONE else with 97-03 4X4 problems check out this link it might save me and you some big BUCKS down the road. http://www.4x4posi-lok.com

revytrucks, what an amazing technical post! Thank you! I was going crazy trying to get the info that you provided, and it answers all of the questions that I had while trying to fix my 4x4 problem. You are a very valuable resource and an ultra capable woman:-X22

Thanks for the link shakeyj98. I may ultimately have to resort to this type of fix.

Awesome!
 

Thanks for your reply! My whole point to posting that was so others could avoid the hours of searching I had to do to figure my problem out. My 4X4 is still working by the way! A little lube and $0 later. Nice!!

revytrucks,

I am still experiencing a problem with the front differential not disengaging when the floor shifter is put in 2 whl high. Here is what I have observed:

1. The solenoid on the right side (passenger side) that has the blue hose is the one that activates the vacuum actuator to engage the front differential.

2. The solenoid on the left side (drivers side) that has the pink hose is the one that activates the actuator to disengage the front differential.

Here is what is happening on my truck:

1. The solenoid on the right side (blue hose) that is used to engage the front differential is always ON. The blue hose is ALWAYS SUCKING no matter what position the floor shifter is in. Consequently, the front diff. is always engaged in 4wd.

2. The solenoid on the left side (pink hose) that is used to disengage the front differential is always OFF. It DOESN'T SUCK no matter what position the floor shifter is in.

In the past, when I parked the truck it would have to cool down before the front differential would finally disengage. I am thinking that the sensor or relay in the transfer case that sends the appropriate signal to the solenoids is defective.

Do you have any part numbers and a name for that sensor in the transfer case?

Hi jackpiner

I was lucky and didn't have to mess with any of the relay/fuse stuff with mine, so I generally avoided it once I found the solenoids were working.
One question -- Does your dash light come on when you shift it into 4X4?

From what I read, when the dash light is on/off when its not supposed to be, this indicates a problem with the relay/sensors/GEM.

If the light goes on when you shift it in and off when you shift it out, I wouldn't be surprised if the problem is just in your disengage solenoid.

Check out the diagram of the system in this forum to see how the system works:

Ford F150 .net &bull; View topic - Vacuum lines From transfer case to solnoids

From what I know, you can rule out problems with the vacuum resorvoir and the engine vacuum becuase you still have vacuum to the one solenoid.

Since there is constant vacuum, I would assume that it is a problem with the activation, but it wouldn;t be a bad idea to check the disengage solenoid. It should have 12V all the time on it, and if not, it may need replacing. Part #: Disengage solenoid 6L3Z-9H465-A (identified by electrical connector rib at 9:00 position)

I think that you are right and there is a problem with the switch, GEM, or the wiring to the GEM. The GEM grounds each solenoid to activate it.

A couple questions:
After the truck cools down and disengages on its own, is there a change in the hose vacuum (ie does the pink have vacuum instead of the blue?). I just want to know why the truck finally disengages...might give clues to why it doesn't disengage!

Also, careful because driving with the differential engaged is like driving with 4X4 on if you are on dry pavement...front wheels are still locked in even though they dont have power. Try not to drive too much like that.

I'll think about this some more and add some later....hopefully you can get it going and don't forget to post how you do it if you manage to!

Thanks

revytrucks,

My 4x4 light is always on and doesn't go off no matter what position the floor shifter is in

I don't think I explained very accurately what the initial symptoms were. When this problem started happening about a year ago, I noticed that sometimes when I shifted out of 4wd and into 2 wheel high it took a minute for the front differential to disengage and 4x4 light to go off. This got gradually worse over time and it would take longer and longer for it to disengage and the 4x4 light to go off. More recently it had not been disengaging unless I shut the truck off and let it sit for a while, then when I restarted it I would notice that it did disengage and the 4x4 light was off.

Presently, the front differential won't disengage at all when shifted into 2 wheel high and the 4x4 light is always on. This is because at the solenoid nipples, I have constant suction on the blue hose (engage solenoid) and no suction ever on the pink hose (disengage solenoid) no matter what position the floor shifter is in.

The diagram in the link you provided is wrong. (Not your fault!) I saw that same one when surfing the web for answers and noticed the error. In actuality, the pink hose (disengage) goes on the plunger side of the actuator to draw the plunger out, thus disengaging the differential. The blue hose goes on the opposite side to draw the plunger into the actuator and engage the differential.

The vacuum actuator on my front differential housing is functioning properly and the plunger moves freely. I actually switched the pink and blue hoses around on it to see if it would make it disengage, and it did! So now I was able to drive the truck to the dealer and I bought the engage solenoid thinking that the one in my truck was stuck in the open position. Well, it is stuck in the open position, but not because it's defective obviously. Installing the new one made no difference.

So now I am wondering if maybe the disengage solenoid is stuck in the closed position? I have vacuum at the bottom nipple(it's supposed to) but none at the top nipple (which is the one with the pink disengage hose on it.) If this one is stuck closed, would that cause the other one to stay open? I hate to waste another $40.00 on something I don't need and can't return.

I'm wondering if a sensor or something is "telling" the engage solenoid to activate even though the floor shifter is in the 2 wheel high position? Maybe a sensor in the transfer case is stuck in the 4wd position? Heating and cooling cycles appear to have been a factor in the past, and the only component that I can think of that heats up and cools down is the transfer case.

jackpiner ---
 

Thanks for the more info. Personally, I would say that the solenoid is probably ok if the 4X4 light stays on all the time. Here is some info I found about testing the solenoids to make sure:

The default setting ground applied to the disengage solenoid. You can test this with a continuity meter. Engage 4x4 and probe the red ground wire to the engage solenoid (closest solenoid to the fender). There should be continuity to ground. Then disengage 4x4 and probe the Gray w/Black stripe ground wire to the disengage solenoid ground wire ( closest solenoid to the engine). There should be continuity. If these circuits check out then test the solenoids. If they don't test OK the 4x4 indicator switch or the relay or the GEM may be defective.

I haven't found exactly what the process is that turns the 4X4 light on and off, however, since both the 4X4 and the light stays on, that somehow the switch in the transfer case is somehow staying on. I am not familiar with this part of the 4X4 system, so I can't really elaborate on what you have found out. I would say that you are right on the money.

What I would reccommend is going to the Ford dealership and asking questions about the sensor. Ask for a part number for it and they will generally help out. It usually works for me.

I'll see what else I can dig up.

revytrucks,

After putting the new engage solenoid in, it made no difference. The front differential was still locked in. However, the truck was well warmed up because I had just gotten back from the dealer. Here's the rub. After letting it cool down overnight, I crawled under the truck and pulled the connector off of the Transmission Range Sensor Switch on the front of the transfer case. It was all clean and shiny. I then started the truck and noticed that the disengage solenoid had activated, thus disengaging the front differential! Yay. Maybe it reset something?

I then reconnected the connector and got into the truck. Everything worked normally again! I drove around and shifted in and out of 4wd with no problems whatsoever. Until about the 10 mile mark, when all of a sudden it started getting finicky. I let the truck cool down and all was normal again. Until it warmed up.

Summary: I think the problem is a bad Transmission Range Sensor Switch. I took it out and noticed it was clean and shiney, but the little ball got stuck when I pushed it in. I think this is the problem. I am calling the dealer tomorrow to see if they have one. I'll report back with my findings.

What exactly is the transmission range sensor switch?

it senses what range the transfer case is in(2hi,4hi,4lo)

This was my problem. I replaced it and all is well.

The Transmission Range Sensor Switch part # 4L3Z 7E440 AB is located on the left front of the transfer case. There is an electrical connector plugged into the switch. This cost me $27.18 (discounted 20% from list price) at the dealership.
Attachment 203915

The ball is spring loaded and you should be able to push it in and it should spring back out smoothly. If it sticks, like in this picture it needs to be replaced.
Attachment 203916


I didn't need the engage vacuum solenoid after all. I have a brand new one if anyone wants it. This is the one that puts the front differential into 4wd. The part # is 6L3Z-9H465-B This cost me $33.75 (discounted 20%from list price) I'll sell it for what I have into it and I'll ship it for free.
Attachment 203917

Attachment 203918

This was an awesome post!!
Great work gathering all this information!