Question about 2003 Ford F150 Regular Cab

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No vacuum at shift motor for 4x4 - 2003 Ford F150 Regular Cab

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CHECK THE HUBS IF IT IS AUTO LOCK 4X4.THERE WILL BE A VACUME LINE BEHIND THE BRAKE ROTOR ON TOP OF THE HUB ASSY.

Posted on Nov 24, 2013

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Posted on Jan 02, 2017

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SOURCE: elec 4 wheel drive light comes on but 4x4 not engaging

change the 2 solenoids on the firewall on the passenger side. they contol the vacum to the acuator.

Posted on Feb 05, 2009

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SOURCE: f250 2004 4x4 not working, vacuum holds on lines

With the hublocks in the AUTO position, the 4x4 ESOF system uses timed vacuum sequences to lock and unlock the wheel ends when switching the instrument panel MSS between 2WD and 4x4 modes. A high vacuum level (222 mm [8.75 in] Hg and greater) is applied to the hublocks to lock the internal spring mechanism that engages (locks) the hublocks for 4x4 mode, and a lower vacuum

level (114 to 184 mm [5.9 to 7.1 in] Hg) is applied to unlock the spring mechanism that disengages (unlocks) the hublocks for 2WD mode.


The vacuum system is actually pretty simple. On the passenger side firewall is an electric vacuum pump. There is a vacuum line coming off of it that goes over to a vacuum reservoir. Also connected to the reservoir is a T fitting with two lines from it. One line goes forward into the cab to the heater controls. The other line enters a loom and goes to the PVH (Pulse Vacuum Hublock) solenoid. This solenoid controls vacuum to the automatic hub locks.

The first tests I would do are pretty simple. With the key in the RUN position, unplug the line at the pump. The pump should start running immediately. Put your finger over the nipple and the pump should stop immediately. This verifies your pump is good.

Once you've done that, I'd hook the pump back up, leave the key in RUN and watch the system for awhile. Maybe 10 to 15 minutes. The pump should run long enough to pull a vacuum in the reservoir and all the lines and then shut off. If the system holds and the pump doesn't come back on, then you've essentially verified that the reservoir, the lines going forward to the heater controls, and the lines going to the PVH solenoid are all good and not leaking.

If the pump cycles back on regularly, then you have a leak somewhere in those lines or the reservoir and you need to start tracing them out to find it. Start at the reservoir, disconnect a line on the pump side, plug it and see that the pump pulls down a vacuum and holds it. Reconnect that line and move down to the next connection and do the same thing. Continue this procedure until you've traced down all the lines. If you get to a point where the pump continues to run, or cycles on and off, then you've found a leak in the last section of line you've tested.

If all of the lines up to the PVH solenoid test good, then you're left with the solenoid itself, the lines from the solenoid to the hubs, or the hub seals. This is where a good hand vacuum pump with a gauge comes in handy. You can attach the pump at the line going down to the hubs, pump up about 14 PSI of vacuum and see if it holds. If it does, then the lines and the hub seals are good. If it doesn't, then start working down towards the hubs, isolating lines to see if they hold vacuum. It is common to find cracked lines going down to the hubs this way. If you get all the way to the hubs, attach your pump to the vacuum nipple on the back of the hub, pump up about 14 PSI and see if it holds. If it doesn't, then that hubs seals are bad and need replacing.

If, in the end, all of your lines and hubs hold vacuum properly, you are pretty much left with the solenoid itself. Attach your vacuum gauge to the line after the solenoid and have someone switch to 4WD. The solenoid should apply about 14-15 PSI for up to 60 seconds. Then have them switch back to 2WD. The solenoid should apply about 7 PSI for about 60 seconds. If neither of these happens then your solenoid is likely bad.

You may want to check the center pin of the solenoid wiring connector for power.

Posted on Mar 01, 2011

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2003 ford f250 superduty 4x4 don't work no indicator light on dash changed4x4 switch module what next?


Check for codes. Usually part stores do it for free. here is how it works.
Principles of Operation

Electronic Shift on the Fly (ESOF) System

The electronic shift on the fly (ESOF) system is an electronic shift system that allows the operator to choose between 2 different 4x4 modes as well as 2-wheel drive. The operator can switch between 2H and 4H mode at speeds up to 88 km/h (55 mph). To engage or disengage 4L, the 4x4 generic electronic module (GEM) requires that the vehicle speed be less than 5 km/h (3 mph), the brake pedal depressed and the transmission in NEUTRAL (or clutch pedal applied on manual transmission vehicles). This system contains pulse vacuum hublocks (PVH). The selector on the hublock, when turned fully counterclockwise to the AUTO position, engages/disengages the hub depending on the driver-selected 4x4 mode of operation. The hublocks also contain a manual override. When the selector is rotated fully clockwise to the LOCK position, the 4x4 vacuum and electronic system used for coupling the front axle to the wheel is bypassed.

The transfer case is equipped with a dual-cone synchronous clutch. This clutch is used to synchronize the front driveline to the rear. All other internals operate in the same manner as the manual shift system. When the mode select switch (MSS) on the instrument panel is turned, the 4x4 module powers the transfer case motor, which activates a shift fork and engages the clutch. When the shift motor reaches the desired position, as determined by the encoder position inputs to the 4x4 module, power to the shift motor is removed. When the transfer case front and rear output shafts are synchronized, the lockup collar mechanically engages the mainshaft hub to the drive sprocket. At this point, the front axle PVHs are engaged. Instrument cluster "4x4" and "Low Range" indicator operation is controlled via hardwired outputs from the 4x4 module.

Electronic Shift Transfer Case

The New Venture Gear NV 273 electronic shift transfer case is a 3-piece aluminium design. The unit transfers engine power from the transmission to the front and rear axles. Under normal driving conditions the unit is in 2-wheel drive high (2H), but when desired, the operator may shift into 4-wheel drive high (4H) or 4-wheel drive low (4L). The transfer case is shifted electronically. The unit is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the mainshaft.

The encoder assembly used for mode indication is of a Hall-Effect type. The system uses a total of 4 independent transistors for mode recognition. Each transistor is associated with a specific range of motor movement. When the circuit to each transistor is closed, a ground path to any of the A, B, C or D encoder pins is accomplished. When the circuit to each transistor is open, the connection to any of the A, B, C, or D encoder pins is pulled to voltage. Mode indication is "decoded" by the 4x4 module based on the varying combinations of signals coming from the transistors.

Hublock Operation

With the hublocks in the Auto position, the 4x4 ESOP system uses timed vacuum sequences to lock and unlock the wheel ends when switching the instrument panel MSS between 2WD and 4x4 modes. A high vacuum level (222 mm or 8.75 in. Hg and greater) is applied to the hublocks to lock the internal spring mechanism that engages (locks) the hublocks for 4x4 mode, and a lower vacuum level (114 to 184 mm or 5.9 to 7.1 in. Hg) is applied to unlock the spring mechanism that disengages (unlocks) the hublocks for 2WD mode. The vacuum signals are supplied to the hublocks by system components, including the 4WD control module or GEM, wiring harness, solenoid, vacuum harness and vacuum seals. As a first step in service, eliminate obvious items such as loose wiring connections, loose vacuum connections or damaged vacuum lines.

Dec 12, 2014 | 2003 Ford F250

2 Answers

Got. A 2003 f150 4x4 got problems with 4 wheel drive locking in and stay in drive shaft turning front wheels not


Operationally vacuum shifts the front axle between 2WD and 4WD mode. The GEM ( Generic Electronics Module ) applies ground to the solenoid needed for the mode selected on the switch ( for ESOF ) or when the transfer case shift lever is moved ( MSOF ).The contact plates in the transfer case signal the GEM that the transfer case is engaged, and the Vacuum solenoids need to be activated ( either 2WD to 4WD or 4WD to 2WD ).

Lift and support the front of the truck so the front wheels are off the ground ( take safety precautions, chock wheels, jack stands, etc )
Key on, engage 4x4 and try to turn the front drive shaft.
- If it turns it is a problem with the transfer case.
- If it doesn't it is a front axle engagement problem ( this is what you seem to have, the transfer case is engaged and will drive the front shaft mine was a key on engine off test ).

- If the front drive shaft does not turn :
•With the truck running ( with front wheel back on the ground ), switch from 2WD to 4WD and back again, the vacuum shift motor should move the lever on the front axle.
sscullys_185.jpg
-- If the vacuum shift motor does not move:
1.Check for vacuum on the lines while shifting between modes. Pink vacuum line is 2WD mode, Light Blue vacuum line is 4WD.
2.Check the fuses for the 4WD system and the solenoids.
3.Check the vacuum lines from the vacuum shift motor to the solenoids on the firewall.
sscullys_187.jpg
4.Check the vacuum lines from the solenoids to the vacuum reservoir box behind the battery.
5.Check the vacuum reservoir box for cracks.
6.Typical solution is the vacuum lines ( to the solenoids or to the vacuum shift motor ) are cracked or the vacuum shift motor has a cracked diaphragm and has water in it.
7.Could be the shift plate contacts in the transfer case are corroded / not making good contact, and not activating the solenoids.
sscullys_186.jpg

Usually the case is cracked vacuum lines from the solenoids, the next common is a cracked vacuum reservoir box, and 1 time I have seen the mount for the vacuum disconnect motor broken ( motor floating free so it could not push against the axle )
sscullys_188.jpg

Aug 28, 2011 | 2003 Ford F150 Regular Cab

1 Answer

I can not get power to the motor to engage my front axle on my 4x4.


Power as in 12 V DC ? if yes, you are not in the correct area, the front axle is locked in and out of 4x4 mode with vacuum.

Operationally vacuum shifts the front axle between 2WD and 4WD mode. The GEM ( Generic Electronics Module ) applies ground to the solenoid needed for the mode selected on the switch ( for ESOF ) or when the transfer case shift lever is moved ( MSOF ).The contact plates in the transfer case signal the GEM that the transfer case is engaged, and the Vacuum solenoids need to be activated ( either 2WD to 4WD or 4WD to 2WD ).


Lift and support the front of the truck so the front wheels are off the ground ( take safety precautions, chock wheels, jack stands, etc )
Key on, engage 4x4 and try to turn the front drive shaft.
- If it turns it is a problem with the transfer case.
- If it doesn't it is a front axle engagement problem.

- If the front drive shaft does not turn :
•With the truck running ( with front wheel back on the ground ), switch from 2WD to 4WD and back again, the vacuum shift motor should move the lever on the front axle.
sscullys_200.jpg
Item #10 in this diagram
sscullys_10.gif
-- If the vacuum shift motor does not move:
1.Check for vacuum on the lines while shifting between modes. Pink vacuum line is 2WD mode, Light Blue vacuum line is 4WD.
2.Check the fuses for the 4WD system and the solenoids.
3.Check the vacuum lines from the vacuum shift motor to the solenoids on the firewall.
4.Check the vacuum lines from the solenoids to the vacuum reservoir box behind the battery.
5.Check the vacuum reservoir box for cracks.
6.Typical solution is the vacuum lines ( to the solenoids or to the vacuum shift motor ) are cracked or the vacuum shift motor has a cracked diaphragm and has water in it.
7.Could be the shift plate contacts in the transfer case are corroded / not making good contact, and not activating the solenoids.
sscullys_199.jpg

- If the front drive shaft turns:
For ESOF system
-- Check the fuses for the transfer case, engine compartment fuse panel, 17 & Cab fuse panel fuses 13 and 23 ( verify with owners manual, 97-97 & 99-03 MY can be slightly different on some items ).
-- Try hitting the transfer case with a dead blow hammer ( do not use a metal hammer, it can damage the transfer case ) to see if the transfer case shift motor is hung up .
-- Check the transfer case connector, to make sure the connector pins are clean and making good contact.
For MSOF systems
-- Check that the shift linkage on the transfer case is moving when the lever is moved from 2W to 4H and 4L.

Jul 30, 2011 | 2000 Ford F150 Flareside SuperCab

1 Answer

2002 dodge Dakota stuck I'n 4 wheel drive so u


The 4x4 is controlled by vacuum. There is a vacuum switch on the top of your transfer case that control the vacuum to the front axle shift motor. The shift motor has 2 ports, when vacuum is applied to one side the shift motor moves the fork one way and when vacuum is applied to the other side, the fork moves the other way.

The first thing I would do is verify the hoses at the transmission cross member are hooked up. Then I would remove the 4 bolts from the shift motor and remove the motor and start the engine and shift in and out of 4x4 waiting 10 seconds before each shift and see if the fork moves.

If it doesn't you will need to check the vacuum connector on top of the transfer case and make sure it is fully attached, if it is, you will need to remove the vacuum connector and check to see if you have engine vacuum on one port(around 15" vacuum). The ports are as follows - one port goes to engine vacuum, one port goes to a vent and the other two go to your shift motor. The hoses that go to the shift motor are bad for getting plugged, so you should use compressed air and see if they are clear.

If everything checks out, you will have to remove the switch on the transfer case and operate it by hand while the engine is running and see if the plunger moves in and out. Sometimes the plungers will stick in!

A vacuum gauge and pump are needed to check the motor and switch. If you don't have one, you might need to borrow one and put a vacuum on the shift motor and see if it holds vacuum. Once you put a vacuum on the shift motor the fork should move and then should pump down and hold a vacuum, if it doesn't hold vacuum, you will need a shift motor.

This is alot of info, but there are many possibilities for this not working and you will have to check all these things to diagnose this.

Jul 27, 2011 | 2002 Dodge Dakota Club Cab

1 Answer

I have a 98 f150 4x4 automatic with the 4x4 shifter on the floor. Wheni shlift into 4x4 the front does not go in to gear.


Lift and support the front of the truck so the front wheels are off the ground ( take safety precautions, chock wheels, jack stands, etc )
Key on ( engine off ), engage 4x4 and try to turn the front drive shaft.
If the front driver shaft turns it is a problem with the transfer case.
If it doesn't it is a front axle engagement problem.

The front axle engagement problems are either rotten vacuum lines from the shift motor solenoids or the vacuum disconnect motor.
The vacuum disconnect motor ( Item #10 )
sscullys.gif
Close up of what it looks like :
sscullys_5.jpg

The vacuum lines run to the solenoids
sscullys_6.jpg

The Pink Vacuum line is the 2WD operation, the Light blue vacuum line is the 4WD operation. You can confirm the operation by applying vacuum at the solenoid, and the Vacuum disconnect motor should move.
If this tests good, check that there is not a crack in the vacuum reservoir behind the battery. The reservoir runs past the check valve ( that is to the intake I seem to recall ) and to a T to both solenoids. If the reservoir is cracked, it cannot supply vacuum to the solenoid and while it is operating correctly, the vacuum is not there to operate the disconnect motor.

The solenoids always have + DCV at them, the GEM controls them by applying ground to the solenoids.

Start by checking the front driver shaft, and work from there. If the front drive shaft spins, you have an issue in the transfer case, that is mechanical ( manual Shift on the Fly - could be hung up. you can try a dead blow hammer on the back of the transfer case, while trying to shift in and out of 4WD. Just be cautious that you do not damage the transfer case by hitting it too hard, too much or with a metal hammer ).

Nov 02, 2010 | 1998 Ford F150 Regular Cab

1 Answer

My 2003 F-150 will not engage the 4-wheel drive when the switch is turned on? Two days ago it worked fine and the light does come on?


Lift and support the front of the truck so the front wheels are off the ground ( take safety precautions, chock wheels, jack stands, etc )
Key on, engage 4x4 and try to turn the front drive shaft.
If it turns it is a problem with the transfer case.
If it doesn't it is a front axle engagement problem.

I am going to guess the drive shaft will not turn, and the problem is the shift disconnect motor on the front axle, or the shift solenoids.
The shift motor looks like this
37bcd6a.jpg

The shift solenoids look like this :
1a11fc1.jpg

You can check the shift solenoids with a vacuum gauge. The blue vacuum line is the 4WD operation, the pink is the 2WD operation. Pull the vacuum line at the shift disconnect motor, and install the vacuum gauge. Shift into 4WD and the vacuum should be on the line, and hold. If not could be the disconnect motor or the vacuum line to the motor.

Could also be the shift motor in the transfer case, but with the 4x4 light on the cluster lighting up, the transfer case should have shifted, the confirm comes from the transfer case to illuminate the 4x4 indicator on the cluster.

Feb 20, 2010 | 2003 Ford F150 Regular Cab

1 Answer

The transfer case will not shift into 4 wheel hi or low 4 wheel drive auto with elect shift


I would suspect the vacuum disconnect motor or the vacuum solenoids for the disconnect motor ( or the vacuum lines ), but best to confirm
Lift and support the front of the truck so the front wheels are off the ground ( take safety precautions, chock wheels, jack stands, etc )
Key on, engage 4x4 and try to turn the front drive shaft.
If it turns it is a problem with the transfer case.
If it doesn't it is a front axle engagement problem.

With the engine running ( and wheel chocked, parking brake on ) have someone shift into 4WD, and watch the shift motor to see if it operates
It is on the front axle, looks like this
85ec248.jpg

If the disconnect motor does not shift, you can check the vacuum on the lines with a vacuum gauge. Blue line is 4WD operation, pink line is 2WD operation.
The vacuum solenoids are on the firewall, and look like this
50a3265.jpg

This is the block diagram for the ESOF vacuum operation of the disconnect motor.
c01c924.jpg

This is assuming you have checked the fuses for the transfercase shift motor, and the vacuum solenoids.

Feb 16, 2010 | 2000 Ford F150 Flareside SuperCab

2 Answers

4wd does not work


Electronic Shift On the Fly (ESOF) Operation
The ESOF system is an electronic shift 4x4 system that allows the operator to choose between two different 4x4 modes as well as 2-wheel drive. The operator can switch between 2WD and 4WD HIGH mode at speed. To engage or disengage LOW Range, the vehicle speed must be less than 5 kph, the brake depressed, and the transmission must be in NEUTRAL.

The transfer case is equipped with an electromagnetic clutch which is located inside the case. This clutch is used to spin up the front drive-line when shifting from 2WD to 4x4 High mode at speed. When the control switch on the instrument panel is turned, the generic electronic module (GEM) recognizes that a shift has been requested and activates the electromagnetic clutch and the relays which power the transfer case shift motor. When the shift motor reaches the desired position as determined by the contact plate position inputs to the GEM, power to the shift relays and motors will be removed. When the transfer case front and rear output shafts are synchronized, the spring loaded lockup collar mechanically engages the main-shaft hub to the drive sprocket. Finally, the front axle collar is engaged and the electromagnetic clutch is deactivated.

Shift Between 2WD and 4x4 HIGH:
Shifts between 2WD and 4x4 HIGH can be made at speed. Listed below are the inputs and outputs needed by the GEM to execute a change between any of these modes.

Feature Inputs:
*4WD Mode Switch (Various resistances).
*Contact Plate Position Inputs A, B, C, D (grounded when closed, open circuit when open).

Feature Outputs:
*4x4 Shift Motor Relay Outputs
*Transfer Case Clutch Relay (grounded when relay is on, open circuit when relay is off).
*4x2/4x4 Vacuum Solenoid (grounded when activated, open circuit when deactivated).
*Cluster Indicators (ground when activated, open circuit when deactivated).

Shifting Into/Out of 4WD LOW:
When shifting into or out of 4WD LOW, the GEM requires that the vehicle speed be less than 5 kph, the brake is applied, and the transmission is in NEUTRAL.

Feature Inputs:
*4WD Mode Switch (Various resistances).
*Contact Plate Position Inputs A, B, C, D (grounded when closed, open circuit when open).
*VSS Sensor (Sinusoid Signal: 0.7V-20V, 2.2 Hz/mph).
Brake Input (battery voltage when brake is depress, open circuit when not activated).
*Transmission Range Sensor (grounded when transmission is in NEUTRAL, open circuit otherwise).
8Start/Clutch Depressed Input

Feature Outputs:
*4x4 Shift Motor Relay Outputs
*4x2/4x4 Vacuum Solenoid (grounded when activated, open circuit when deactivated).
*Cluster Indicators (grounded when activated, open circuit when deactivated).

4WD Mode Switch
A rotary switch allows the vehicle operator to choose between 2WD, 4WD HIGH, and 4WD LOW modes of 4x4 operation.

GEM Module
The Generic Electronic Module (GEM) controls the operation of the 4x4 system

Vehicle Speed Sensor
The vehicle speed sensor (VSS), mounted in the rear of the transfer case, informs the GEM of the vehicle speed.

Transfer Case Shift Motor Sense Plates

The shift motor sense plate, an integral part of the electric shift motor, informs the GEM to the positions of the transfer case

Transmission Range Sensor
Located on the left side of the transmission, this sensor informs the GEM when the transmission is in the NEUTRAL position.

Electric Shift Motor
The electric shift motor, mounted externally at the rear of the transfer case, drives a rotary cam which moves the mode fork and range fork within the transfer case to select between the 2WD, 4WD HIGH, and 4WD LOW positions.

4x4/4x2 Vacuum Solenoids
These two solenoids are attached to the upper RH side of the engine compartment dash, and alternately route vacuum to the vacuum motor which engages/disengages the center axle disconnect collar in the front axle assembly.

4x4 Shift Motor Relay
A module containing two relays which under the control of the GEM, shift the transfer case shift motor between the 2WD, 4WD HIGH, and 4WD LOW modes.

Transfer Case Clutch Relay
An electromechanical relay is used to activate the transfer case clutch within the transfer case.

Good luck and hope this helps,but start with the simple and check the fuses and wire harness. Both white/light blue stripe wires should have 12V in run. The GEM will ground the left side (closest to engine) solenoid to disengage the front axle. It will ground the the right side solenoid (closest to fender) to engage the front axle. If the GEM doesn't see Neutral it will not let the truck come out of 4Lo. If the GEM had water leaking on it it may well be the root of the problem. The shift motor only has power when the GEM sends it a signal to move the shift lever. Once the shift is completed the motor shuts off. There are 2 wires that control the shift motor. A yellow and an orange. The GEM alternates between 12v and Ground to these wires to control which way the motor turns. The GEM uses the transfer case shift relay module to control the power to the motor. There are contact plates inside the shift motor assembly that indicate the position that the shift lever is in. This is what the GEM used to know what the T-case is doing. Any one of these components can fail.







Jan 10, 2010 | 2002 Ford Explorer

2 Answers

1998 Ford f150 4x4 intermittant clapping sound front axle area


The vacuum shift motor ( actually a diaphragm ) is a vacuum to move the lever one direction ( i.e. 4WD ) and then vacuum to move the other direction ( i.e. back into 2WD ).

You can shift into 2WD and remove the vacuum lines and plug them to remove this, if you think the vacuum shift solenoids are getting ground from another source and shifting the front axle, or just unplug the connector on the shift solenoids. The GEM activates the Shift solenoids by applying ground to them.
1b857e9.jpg

I would have to agree with papa_11069 that the problem is in the front u-joints.

Dec 30, 2009 | 1998 Ford F150 Regular Cab

1 Answer

Elec 4 wheel drive light comes on but 4x4 not engaging


change the 2 solenoids on the firewall on the passenger side. they contol the vacum to the acuator.

Jan 27, 2009 | 1999 Ford F150 Regular Cab

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