Will not engage 4WD

Ok you will need to check the front axle vacuum hoses and such for any leaks and I would also check the transfer case shift motor on the back of the t-case. here is a pic of the vacuum routing for the front differential followed by a pic of the t-case shift motor.

Four wheel drive will not engage regardless of switch in four wheel drive or all wheel drive.

check fuses and relay under hood then scan for codes. may be a bad motor on transfer case, switch, TCM.

1997 Ford Expedition V8 Four Wheel Drive Automatic

My 97 expedition doesn't engage the 4wd when I turn it on. The lights indicate 4wd, but it's not engageing. I have read a lot about the soleniod... where it is and how do I check it? Any other ideas would be appreciated.

Hi:
The actuator is on the transfer case. check to see if you are getting power to it when you switch to 4wd. If you are, the actuator is most likely bad.

Joe

when I turn the switch for 4wd nothing happens no dash lite no relay click , nothing checked fuse and fuse is good. looks very involved to get the switch out to check it. any suggestions? thanks

Hi:
Before removing the switch, check to see if power is getting to the actuator on the transfer case.

'97 Expedition- when I switch into AWD,4W, 4L it will not engage the front wheels, I can here an engageing noise in 4WL and it shifts to Low but still the front wheels do not engage.
Thanks for you help

The allwheel drive lights up, the low and hi don't. It makes clicking noises but does not engage. Is there a vacuum switch or something common that it could be? A friend has a explorer that a vacuum module or plug underneath the car went out and the 4 wheel would not engage. Mine has worked but the 4 hi went and then the low and allwheel went, but the allwheel light comes on, the rest don't. It drives good in 2 wheel, but I'm burried in snow and have to work. Thanks, Mark Wakefield

mounted on the transfer case there is a electric shift motor. check to make sure it is working. since you do hear a click then I would say that the motor is working but not the clutch inside. before taking it apart make sure it is getting power when you turn on the 4 wheel drive. check the wiring make sure everything is connected.

I have replaced the DC motor on transfer case that switches to 4H and 4L, and I even switched the transfer case manually with a pair of pliers while I had the DC motor/limit switch unit off, and the transfer case seems to work just fine. I think there must be a module or something that is not working. Before it finally quit completely, it used to go into 4H but only after the light would flash repeated for several minutes. That's the reason I thought it would be the DC motor/limit switch assembly on the transfer case. Anyone know where the dash switch inputs go to, and if there is a module or shift module of some sort that would possibly be bad? Thanks for any help you can give! --eric

Ok, I've checked the selector switch, ford calls it the function selector switch. It seems to be working fine. It seems to be a variable resistance type switch where each switch position is a different resistance. Is this correct? So, in 2wd it reads between term 2-3 4vdc, and in A4wd it reads 3vdc, and in 4H it reads 2vdc, and in 4L it reads 1vdc. This makes sense, being that there aren't enough wires to power the light on the switch and give a separate set of contacts for each switch position, there are only 4wires. Anyway, it seems like the switch is working just fine, but there must be some kind of shift control module that senses these voltages and switches the transfer case motor according to the resistance and whatever other permissives and requirements the module needs? Wow! What I wouldn't give for a good old fashioned lever that goes 'clunk' when the transfer case goes into 4H or 4L... Please help asap as the snow is flying here in WY.

DESCRIPTION & OPERATION The electronically controlled 44-05 transfer case has A4WD (automatic), 4WD HIGH and 4WD LOW ranges. Transfer case operation is conducted by 2 motor driven shift forks (2WD to 4WD and 4WD HIGH to 4WD LOW) and internal electromagnetic multi-disc clutch assembly (automatic operation). When in A4WD, system uses 2 hall effect type front and rear drive shaft speed sensors to compare front and rear drive shaft speeds. When drive shaft speeds differ by a predetermined amount the Generic Electronic Module (GEM) activates internal clutch to lock transfer case and equalize drive shaft speeds. At rest and cruising conditions, the GEM activates the transfer case clutch at a minimum duty cycle. The clutch duty cycle is longer when slipping of front or rear axle is detected, during heavy acceleration or with very light throttle at speeds greater than 40 MPH. MODULE LOCATION Generic Electronic Module (GEM) is mounted on fuse block, below left side of dash panel. INPUT DEVICES Brake On/Off (BOO) Switch The PCM receives a signal from the BOO switch when the brake switch is operated. The GEM and PCM are linked by a communication network. When shifting into or out of LOW range, the GEM requires brake pedal to be depressed. Clutch Pedal Position (CPP) Switch The PCM receives a signal from the CPP switch when the clutch pedal is depressed. The GEM and PCM are linked by a communication network. When shifting into or out of LOW range, the GEM requires clutch pedal to be depressed. Drive Shaft Speed Sensors Hall effect type sensors monitor front and rear drive shaft speeds and input information to GEM. This input is used primarily to control A4WD (automatic) operation. 4WD Mode Switch Instrument panel mounted switch sends input signal to GEM pertaining to commanded transfer case range. Shift Motor Sense Plate The shift motor sense plate is an integral part of the electric shift motor. The sense plate sends shift motor position input to GEM. Throttle Position (TP) Sensor The TP sensor is a potentiometer mounted to the engine throttle body. The PCM receives a signal from TP sensor relaying throttle plate position. The GEM and PCM are linked by a communication network. Signal is used by the GEM to control A4WD clutch. Transmission Range Switch The TR sensor is a digital type. The PCM monitors a series of step down resistors in TR sensor that act as a voltage divider. The voltage signal corresponds with position of transaxle range selector lever. The GEM and PCM are linked by a communication network. The TR sensor also contains neutral/start and backup light circuits. Malfunction of TR sensor may cause transfer case not to shift. Improper transmission shifting or shift selection and no engine cranking may also result. Vehicle Speed Sensor (VSS) The VSS is a magnetic pickup that sends output speed signal to the PCM. The GEM and PCM are linked by a communication network. When shifting into or out of LOW range, the GEM requires vehicle speed to be less than 3 MPH. OUTPUT DEVICES Transfer Case Clutch Relay Pulse width modulated signal operated relay that operates internal electromagnetic clutch. 4WD Shift Motor Relay Actuates electric shift motor mounted to transfer case. Shift motor drives a rotary cam which moves mode fork and range fork inside transfer case. 4WD/2WD Vacuum Solenoids Both solenoids are attached to upper RH side of engine compartment dash panel. Solenoids alternately route vacuum to vacuum motor which engages/disengages center axle disconnect collar in front axle assembly. See Fig. 1 . Fig. 1: 4WD Front Axle Vacuum Diagram
11/14/2009 http://www.ondemand5.com/mric/common/asp/Article.aspx?MOD=REPART&YEAR=1 ...
TEST A: A4WD INDICATOR FLASHES WHEN A4WD MODE IS SELECTED 1. Check Ignition States; Monitor GEM PID IGN_GEM - Turn ignition off. Connect NGS tester. Monitor Generic Electronic Module (GEM) Parameter Identification (PID) Ignition Switch Status (IGN_GEM) while turning ignition switch through START, RUN, OFF and ACC positions. If values agree, go to next step. If values do not agree, see appropriate STEERING COLUMN SWITCHES article in the ACCESSORIES/SAFETY EQUIPMENT section. 2. Retrieve DTCs - Retrieve and document continuous DTCs. Clear continuous DTCs. Retrieve on-demand DTCs. If DTCs are recorded, go to appropriate step(s). See DTC/TEST OR STEP table. If no DTCs are retrieved, go to next step. NOTE: Vehicle must be driven in A4WD at 30 MPH or greater and/or encounter a slip condition before A4WD indicator light will flash for certain faults. NOTE: In next step, if DTC B1342 is retrieved, replace GEM. Clear DTCs and retest system.

Hi,
I have this same issue. What is the name of the vacuum solenoid so I can buy this part. I looked on www.fordparts.com and don't see it.

Thanks,
Paul

1998 ford expedition A4WD OR 4X4 DOESN'T ENGAGE JUST HEAR A CLICKING SOUND BUT IT DOESN'T ENGAGE

Have you checked to see if there is power to the actuator on the transfer case? If there is, the actuator is usually the first thing to go bad.

Let me know.
Joe

1998 expedition 4wd/AWD is not engaging.dash light indicators work but systems do not engage.Worked last year?

is the front driveshaft from transfer case turning? most problems are related to front vacuum operated engage system. bad vacuum lines or actuator.

could also be transfer case motor. check all your plugs/connections

check your vacuum solenoid on the firewall behind battery pass side. if it is not not the newer model that is water sheilded you should replace it they are only 25 at dealer.(most) if it is not working you will not engage drive.

The lights on the switch on the dash are showing 4AWD 4X4 and 4L.
When I move the switch I do hear a loud Clunk, however the axles are not engaging. I replaced both solenoids on the firewall.

A friend looked at it for me and I hope to repeat what he told me. . .He took the cover off the differential, manually pushed the fork and it engaged easily. He then checked the solenoids on the firewall and one of them (passenger side) wasn't working. (He used a vacuum hose to jump between the two and he said it worked) So I replaced that solenoid but it is STILL not engaging.

I do have vacuum at both of the solenoids

ANY HELP OR SUGGESTIONS will be greatly appreciated.

Have you replaced the vacuum hoses? If there is a leak, you may have vacuum but not enough.

Let me know.

The 4wd will not engage with the dashboard switch. The lights on the switch do not come on and there are no noises made. Seems to be stuck in 2wd. I have checked all the fuses and they are good. Anyone have any ideas??? Thanks in advance.

What you need to do is check to see if the 4wd actuator on the transfer case is getting power when you switch to 4wd. If it is, chances are the actuator is bad. If no power is there, then we will need to check wiring to the switch and the switch itself.

Let me know what you find.

Joe

My 1998 Ford Expedition will shift into 4X4 high, but will not go into 4X4 Low. Any help in fixing this would be appreciated.

Chances are either you are not getting power to the actuator from the switch to shift into the 4lo or the actuator is bad. You need to check to see if the actuator is getting power when you push the button for 4lo.

Let me know what you find.

joe

I think the 4x4 module is bad in my truck. Sometimes it sticks in 4x4 and sometimes it won't go into 4x4. But mostly I think it is stuck in AWD. So where can I find the module to change it,and how much will it cost me?

expensive guess. i would look at the motor on the case before the gem module.
The GEM controls the following features:

Wipers/washers (front/rear).
Warning chimes.
Battery saver.
Illuminated entry and courtesy lamps.
Driver power window.
Accessory delay.
4-wheel drive.
REMOVAL




Disconnect the battery ground cable.

CAUTION: Electronic modules are sensitive to electrical charges. If exposed to these charges, damage may result.

Remove the steering column opening cover.




Remove the (A) bulkhead electrical connectors from the (B) instrument panel fuse junction panel.




Remove the (A) instrument panel fuse junction panel bolts and remove the (B) interior fuse junction panel nuts.




Disconnect the (A) GEM electrical connectors from the (B) GEM.
it is pricy with the part, labor and programming.

get a real opinion from a shop first.

Roy



Remove the screws and the GEM.

My vehicle does not engage the 4 wheel drive when AAWD is selected. No problem going into full four wheel drive.I would like to know where the control is for AAWD,on the tranny, near the rear axle, ? I have spoken with two different mechanics about this and they were both vague with their answers. Is it a big secret or are they unfamiliar with that type of drive? If it is electrical I can at least check the circuits and if it is replacable I can probably change it myself. Can you tell me where to find this control?

Actually, there are two speed sensors on the transfer case that determine if the rear wheels are turning faster than the front. It they do, the speed sensor sends a signal to the PCM whch engages the 4wd. I believe on your year vehicle there is one both in the front and rear of the transfer case.

Let me know if you can't find them.