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2008 Ford F250 No 4x4 no Lights no nothing?? HELP!!

6.4L Power Stroke Diesel Engine fitted to 2008 - 2010 F250, F350 and F450 pickup trucks and F350 + Cab Chassis

2008 Ford F250 No 4x4 no Lights no nothing?? HELP!!

Old 11-25-2013, 10:52 AM
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Heres some info i picked up on another Forum, hope it helps

4x4 operation

The four-wheel drive electronic shift on the fly feature
electrically shifts the vehicle transfer case between 2WD, 4X4 HIGH, and 4X4 LOW. The
system mode is selected by the operator through a three-position rotary switch
on the instrument panel. The operator is informed which mode the system is in
by two cluster indicator lamps, one for 4WD HIGH, and one for 4WD LOW (in 4WD
LOW, both the lamps are on). Shifts into 4X4 HIGH can be made at any speed. When
shifting into or out of LOW range, the generic electronic module (GEM) requires
that the vehicle speed be less than 5 km/h (3 mph), the brake applied, and the
transmission in NEUTRAL (A/T) or the clutch pedal be depressed (M/T). (The
digital transmission range (TR) sensor informs the GEM when the transmission is
in the NEUTRAL range position.) The
Electronic shift motor is mounted externally on the transfer case. It drives a
rotary cam which moves the mode fork and the range fork within the transfer
case between the 4X4 HIGH, 4X4 LOW, and 2WD range positions.
The 4X4 shift motor uses two relays which, under control of the GEM, shift the
transfer case shift motor between 4X4 HIGH, 4X4 LOW, and 2WD modes.

The GEM accomplishes shifts system modes by interpreting inputs from:
4X4 selector switch.
Vehicle speed signal (transmitted from the ABS system).
Transfer case.
Brake switch.
Digital transmission range (TR) sensor (automatic transmission).
Clutch pedal position switch (manual transmission).
Ignition switch.
Based on these inputs, the GEM controls the shifts into 2WD, 4X4 HIGH, or 4X4
LOW with the following outputs:
Low to high relay.
High to low relay.

Vacuum hub lock solenoid.
Transfer case shift motor.

The ESOF system has a feature which allows the driver to override the vacuum
operated hubs. When the front hubs are
manually turned to the LOCK position, the hubs are locked at all times, overriding the vacuum operated system. If the front hubs are manually turned to
the AUTO FREE position, the hubs can only be locked by turning the 4WD mode
switch to one of the 4WD positions.
If the front hubs are unable to be unlocked by use of the 4WD mode switch, the
hubs may be unlocked by turning the manual locking hub from the
AUTO FREE position to the LOCK position and back to AUTO FREE.

Check for power at fuse #20 or #21, GEM FUSE and Stater interupt
relay. What could happen to cause no power to be going thru fuse, and the fuse
is not blown?

Looks like there is a fuse going to the GEM 4WD control unit, that also powers the
indicator lights. Check that.

Testing the GEM

Central junction box is the interior fuse panel in front of your left knee and the
connectors are on the back of it.

The Generic electronic module is the module which controls the 4x4
and is mounted to the back of the CJB.

To monitor pids you must use a scan tool and bring up items to
check including ignition switch position

Just cause it controls it
doesn't mean that will be your problem. The GEM gets a signal from the 4x4
switch and controls the transfer case shift relay
module which shifts the transfer case. So you've not only got the GEM but the
switch and t-case shift relay module and all the wiring and several fuses that can cause the problem.
So now you've got to rule things out. First things first, check fuse 17 under
the hood and fuse 12 under the dash. Then I would use a volt meter to first check that there is power at pin 3 then measure
the resistance between the two dark blue wires at the switch, pin 3 and pin 2.
The three positions of the switch should read 3.9k, 1.1k and 360 ohms. If they
aren't then you have a bad switch.

If the switch is good you need to make sure the GEM is outputting the ground
signals to activate the relay that shifts the t-case motor. Orange/light blue
is the wire for high and brown/white is the wire for low, they should be pin 16
and 17. Check those two wires for voltage when the switch is in those
positions. You should check them both at both high and low just in case i'm
wrong about which is high and low. If neither of them have voltage that doesn't
mean it's bad. The wires should be nothing or power at rest and ground in high
or low so take your meter and again set to ohms put one lead on a good ground
and probe the wires with the other. In high and low you should read 0 ohms on
the orange in high end brown in low. if the wires are going to ground the GEM
is good and you need to move on to the relay.

The connector pins. Where the wires go into the connector. You
need to test everything with the connectors connected. Back probe the wires at
the pins right at the connector.

Sometimes you need something small like a paper clip to stick into
the back of the connector so you can get the reading. As you can tell it's not
exactly a basic diagnosis. What really sucks is that the shift relay module is
up in the dash so that
shift relay module is that lil black box in the center of the dash kinda above
the radio which involves taking almost the entire dash apart
Old 11-25-2013, 08:04 PM
highmarkxx is offline
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Thanks. Are the following for a 2008-2010 or a older model? I didn't know there was a fuse box on the left side interior. I've checked the out side driver fuses under the good and the fuse in the kick panel on the passenger side inside the truck. I've replaced the switch and transfer case motor with no luck. I have power at the back of the selector. But no power down at the transfercase motor.
Old 12-17-2018, 12:09 PM
Noah Ledbetter
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2009 f250

where is the 4x4 shift module located or do these trucks just have relays?
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