2003 Expedition/Navigator Workshop Manual
SECTION 308-07A: Four Wheel Drive (4WD) Systems
DIAGNOSIS AND TESTING
Four Wheel Drive (4WD) Systems
Page 1 of 18
2003 Expedition/Navigator Workshop Manual
Procedure revision date: 04/13/2006
Printable View (375 KB)
Refer to Wiring Diagrams Cell 24, Engine Controls for schematic and connector information.
Refer to Wiring Diagrams Cell 23, Engine Controls for schematic and connector information.
Refer to Wiring Diagrams Cell 34, All-Wheel Drive for schematic and connector information.
Refer to Wiring Diagrams Cell 59, Generic Electronic Module for schematic and connector information.
Special Tool(s)
73III Automotive Meter
105-R0057 or equivalent
Worldwide Diagnostic System (WDS)
418-F224
New Generation STAR (NGS) Tester
418-F052 or equivalent scan tool
Vacuum Pump
014-R1054 or equivalent
Principles of Operation
The automatic four-wheel drive (A4WD) system is an electronic-shift 4WD system that allows the operator to choose between 2WD and three different 4WD modes. The
operator can switch between A4WD and 4WD HIGH modes at any speed. To engage or disengage 4WD LOW range, the vehicle speed must be less than 5 km/h (3.1
mph), the brake pedal must be pressed and the transmission must be in NEUTRAL.
Wheel slip is sensed using one axle shaft speed sensor on each axle. Based on throttle position and wheel slip, a pulse width modulated (PWM) signal is transmitted to
the transfer case clutch when a predetermined slip-threshold is exceeded.
The 4WD control module will provide the IVD brake system with current clutch duty cycle and whether or not IVD may command the clutch duty cycle.
The brake subsystem sends the following information signals to the 4WD system:
occurrences of brake events and failures (for additional information, refer to Section 206-09.)
steering wheel angle status (for additional information, refer to Section 206-09.)
average rear wheel speed (for additional information, refer to Section 206-09.)
average front wheel speed (for additional information, refer to Section 206-09.)
delta front wheel speeds (for additional information, refer to Section 206-09.)
A concern with any of the above listed brake system signals will affect operation of the 4WD system.
The throttle position output signal is provided to the 4WD control module from the powertrain control module (PCM). This signal is used by the 4WD control module in
controlling the 4WD clutch.
The shift motor sense plate, an integral part of the gearmotor encoder assembly, informs the 4WD control module of the transfer case position.
The digital transmission range (TR) sensor is located on the LH side of the transmission. This sensor informs the 4WD control module when the transmission is in
NEUTRAL.
The electric shift motor is mounted externally to the gearmotor encoder assembly at the rear of the transfer case. It drives a rotary cam which moves the mode fork and
range fork within the transfer case between the HIGH range (A4WD, 4WD HIGH) and 4WD LOW range positions.
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Page 2 of 18
The 4WD shift motor is controlled by the 4WD control module which shifts the transfer case shift motor between HIGH range (A4WD, 4WD HIGH), and 4WD LOW
modes.
The solid-state clutch is duty-cycled by the 4WD control module to activate the 4WD clutch within the transfer case.
In the A4WD system, the 4WD control module varies the torque sent to the front driveline by controlling the transfer case clutch. At rest and under cruising conditions,
the 4WD control module activates the transfer case clutch a minimum duty cycle (percentage of time the clutch is turned on), which allows for the slight difference
between the front and rear driveshafts which normally occurs when negotiating a corner on dry pavement. Under any of the following conditions, the 4WD control
module will increase the duty cycle in order to prevent or control slip:
slip is detected
heavy acceleration (throttle position)
Feature inputs:
brake ON/OFF switch
mode select switch (MSS)
digital TR sensor (automatic transmission only)
vehicle speed signal (transmitted from the ABS module)
front and rear driveshaft speed sensors
throttle position information (transmitted from the PCM)
gearmotor encoder contact plate position inputs A, B, C, D
Feature outputs:
solid state clutch (pulse width modulated signal)
4WD LOW indicator
4WD shift motor outputs
Shifts between A4WD and 4WD HIGH can be made at any speed. Listed below are the inputs and outputs needed by the 4WD control module to execute a change
between any of these modes.
Feature inputs:
front and rear driveshaft speed sensors
vehicle speed signal
throttle position information
4WD Mode Select Switch (MSS)
Feature outputs:
4WD shift motor outputs
solid state clutch (pulse width modulated signal)
4WD HIGH switch indicator
When shifting into or out of LOW range, the 4WD control module requires that the vehicle speed is less than 5 km/h (3 mph), the brake is applied, and the transmission
is in NEUTRAL.
Feature inputs:
throttle position information (transmitted from PCM)
MSS
gearmotor encoder contact plate position inputs A, B, C, D
vehicle speed signal (transmitted from ABS module)
brake ON/OFF (BOO) switch input (battery voltage when brake pedal is depressed, open circuit when not activated)
digital TR sensor (ground when transmission is in NEUTRAL, open circuit otherwise)
Feature outputs:
4WD shift motor outputs
4WD LOW switch indicator
solid state clutch (pulse width modulated signal)
Inspection and Verification
1. Verify the customer concern.
2. Visually inspect for obvious signs of mechanical or electrical damage.
Visual Inspection Chart
Mechanical
Axle shafts and universal joints
Driveshaft and universal joints
Fluid leaks
Matching tire size
Electrical
Central junction box (CJB) fuses:
11(10A)
115 (30A)
20 (30A)
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Page 3 of 18
4WD control module
Wiring harness
MSS
Gearmotor encoder assembly
Connector(s)
Circuitry
3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
4. If the cause is not visually evident, connect the diagnostic tool to the data link connector (DLC) located beneath the instrument panel and select the vehicle to be
tested from the diagnostic tool menu. If the diagnostic tool does not communicate with the vehicle:
check that the program card is correctly installed.
check the connections to the vehicle.
check the ignition switch position.
5. If the diagnostic tool still does not communicate with the vehicle, refer to the diagnostic tool operating manual.
6. Carry out the DATA LINK DIAGNOSTICS test. If the diagnostic tool responds with:
CKT930, CKT914, CKT 915 and CKT70= ALL ECUS NO RESP/NOT EQUIP, refer to Section 418-00.
NO RESP/NOT EQUIP for 4WD control module, go to Pinpoint Test B.
SYSTEM PASSED, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs and carry out the 4WD control module selftest.
7. If the DTCs retrieved are related to the concern, go to the 4WD Control Module Diagnostic Trouble Code (DTC) Index to continue diagnostics.
4WD Control Module Diagnostic Trouble Code (DTC) Index
DTC
Description
Source
Action
B1317
Battery Voltage High
4WD control
module
CHECK the battery and charging system. REFER to Section 414-00.
B1318
Battery Voltage Low
4WD control
module
CHECK the battery and charging system. REFER to Section 414-00.
B1342
ECU is Defective
4WD control
module
CLEAR the DTCs. REPEAT the 4WD control module self-test. If DTC B1342 is retrieved, INSTALL a
new 4WD control module. REFER to Four-Wheel Drive (4WD) Control Module in this section. CLEAR
the DTCs. REPEAT the self-test.
B2105
Throttle Position Input Out of Range
Low
4WD control
module
GO to Pinpoint Test B.
B2106
Throttle Position Input Out of Range
High
4WD control
module
GO to Pinpoint Test B.
C1728
Transfer Case Unable to Transition
Between 2H and 4H.
4WD control
module
GO to Pinpoint Test C.
C1729
Transfer Case Unable to Transition
Between 4WD HIGH and 4WD LOW
4WD control
module
GO to Pinpoint Test D.
C1979
IWE Solenoid Circuit Failure
4WD control
module
GO to Pinpoint Test F.
C1980
IWE Solenoid Short to Battery
4WD control
module
GO to Pinpoint Test F.
P1812
Transmission 4-Wheel Drive Mode
Select Circuit Failure
4WD control
module
GO to Pinpoint Test D.
P1815
Transmission 4-Wheel Drive Mode
Select Short Circuit to Ground
4WD control
module
GO to Pinpoint Test A.
P1824
Transmission 4-Wheel Drive Clutch
Relay Circuit Failure
4WD control
module
GO to Pinpoint Test A.
P1826
Transmission 4-Wheel Drive Low
Clutch Relay Short Circuit to Battery
4WD control
module
GO to Pinpoint Test A.
P1827
Transmission 4-Wheel Drive Low
Clutch Relay Short Circuit to Ground
4WD control
module
GO to Pinpoint Test A.
P1849
Transmission Transfer Case Contact
Plate A Short Circuit to Ground
4WD control
module
GO to Pinpoint Test D.
P1853
Transmission Transfer Case Contact
Plate B Short Circuit to Ground
4WD control
module
GO to Pinpoint Test D.
P1857
Transmission Transfer Case Contact
Plate C Short Circuit to Ground
4WD control
module
GO to Pinpoint Test D.
P1861
Transmission Transfer Case Contact
Plate D Short Circuit to Ground
4WD control
module
GO to Pinpoint Test D.
P1867
Transmission Transfer Case Contact
Plate General Circuit Failure
4WD control
module
GO to Pinpoint Test D.
P1891
Transmission Transfer Case Contact
Plate Ground Return Open Circuit
4WD control
module
GO to Pinpoint Test D.
U1900
CAN Communication BUS Fault
4WD control
module
Section 418-00.
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Page 4 of 18
U1950
UBP Communication BUS Fault
4WD control
module
Section 418-00.
U2023
External Node Fault
4WD control
module
Section 418-00.
U2306
Invalid UBP Data From Instrument
Cluster (Node 60)
4WD control
module
Section 418-00.
U2226
Invalid UBP Data From PCM (Node
10)
4WD control
module
Section 418-00.
—
For All Other DTCs
4WD control
module
REFER to Section 419-10.
Functional Test — Electronic Shift
PINPOINT TEST A: ELECTRONIC SHIFT FUNCTIONAL TEST
CAUTION: The function test must be carried out on a hard surface in a vacant area without traffic.
Test Step
Result / Action to Take
A1 CHECK FOR 2WD INDICATED
Make sure the hublocks are in the AUTO position.
Start the vehicle and allow to idle.
Apply the brake pedal and hold.
For automatic transmission, shift to NEUTRAL.
Turn the mode select switch (MSS) to 2WD while
holding the shift conditions.
Observe the 4X4 and 4X4 LOW indicators.
Are both indicators off?
Yes
GO to A3.
No
GO to A2.
A2 CHECK FOR THE PRESENCE OF 4X4
CAUTION: Make sure there is a clear area
behind the vehicle before backing up.
Shift the transmission to REVERSE and back the
vehicle up 3 meters (10 feet) to relieve driveline
wind-up.
Drive the vehicle forward for 3 meters (10 feet) and
stop.
Press the brake pedal and hold.
For automatic transmission, shift to NEUTRAL.
Execute tight turns on a hard surface.
Check for the presence of driveline wind-up and tire
scuff.
Is driveline wind-up and tire scuff present?
Yes
RETRIEVE 4WD Control Module self-test DTCs. If a self-test DTC related to the concern is
retrieved, REFER to the 4WD Control Module Diagnostic Trouble Code (DTC) Index in this
section. If no DTC is retrieved, REFER to Section 308-07B and REPAIR the transfer case as
necessary.
No
If the 4X4 indicator is ON, GO to Pinpoint Test E. If the 4X4 indicator is OFF, GO to A3 .
A3 CHECK INDICATOR PROVE-OUT
Ignition OFF.
turn the ignition switch to start and observe the 4X4
and 4X4 LOW indicators for prove-out.
Did the indicators prove out?
Yes
GO to A4.
No
REPAIR the instrument cluster as necessary. REFER to Section 413-01.
A4 VERIFY SHIFT TO 4X4
Turn the MSS to 4X4.
Listen for relay clicks and gearmotor operation.
Wait for 20 seconds after the MSS is turned to 4X4.
Is the 4X4 indicator ON?
Yes
GO to A6.
No
GO to A5.
A5 ATTEMPT MECHANICAL ASSIST ENGAGEMENT
Drive the vehicle above 8 kmh (5 mph) for at least 20
seconds.
Stop the vehicle.
Observe the 4X4 indicator.
Is the 4X4 indicator on?
Yes
GO to A6.
No
RETRIEVE the 4WD control module self-test DTCs. If a self-test DTC related to the concern is
retrieved, REFER to the 4WD Control Module Diagnostic Trouble Code (DTC) Index in this
section. If no DTC related to the concern is retrieved, GO to Pinpoint Test D.
A6 CHECK FOR MECHANICAL ENGAGEMENT OF 4X4
Drive the vehicle for two minutes above 16 kmh (10
mph).
Execute tight turns on a hard surface.
Check for the presence of driveline wind-up and tire
scuff.
Is driveline wind-up and tire scuff present?
Yes
GO to A9.
No
4X4 did not mechanically engage. RETRIEVE 4WD control module self-test DTCs. If a self-test
DTC related to the concern is retrieved, REFER to the 4WD Control Module Diagnostic Trouble
Code (DTC) Index in this section. If no DTC related to the concern is retrieved, GO to A7 .
A7 CHECK FOR FRONT AXLE ENGAGEMENT
Raise and support the front tires off the ground until
they can be spun freely. Refer to Section 100-02.
Rotate the left front tire one revolution forward and
one revolution backward while observing the left
Yes
GO to A8.
No
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2003 Expedition/Navigator Workshop Manual
front axle shaft and universal joint.
Rotate the right front tire one revolution forward and
one revolution backward while observing the right
front axle shaft and universal joint.
Did both front axle shafts rotate?
Page 5 of 18
GO to Pinpoint Test E.
A8 CHECK FOR FRONT AXLE/DIFFERENTIAL
ENGAGEMENT
Rotate the front driveshaft.
Does either front axle shaft turn?
Yes
GO to Pinpoint Test B.
No
REPAIR the front differential or axle as necessary. REFER to Section 205-03.
A9 CHECK FOR CORRECT INDICATOR OPERATION
ON 4X4 LOW ENGAGEMENT
While driving the vehicle forward above 8 kmh (5
mph), turn the MSS to 4X4 LOW while observing the
indicators for five seconds.
Shift the MSS to 4X4.
Stop the vehicle and apply the parking brake.
For automatic transmission, shift the transmission to
PARK and release the brake pedal.
Did the 4X4 LOW indicator stay off?
Yes
GO to A10.
No
RETRIEVE 4WD control module self-test DTCs. If a self-test DTC related to the concern is
retrieved, REFER to the 4WD Control Module Diagnostic Trouble Code (DTC) Index in this
section. If no DTC related to the concern is retrieved, refer to Section 413-01.
A10 CHECK THE 4X4 LOW INDICATOR ON IN ERROR
Turn the MSS to 4X4 LOW.
Apply and hold the brake pedal.
Is the 4X4 LOW indicator OFF?
Yes
GO to A11.
No
RETRIEVE 4WD control module self-test DTCs. If a self-test DTC related to the concern is
retrieved, REFER to the 4WD Control Module Diagnostic Trouble Code (DTC) Index in this
section. If no DTC related to the concern is retrieved, refer to Section 413-01.
A11 CHECK THE 4X4 LOW INDICATOR FOR ON IN 4X4
LOW
For automatic transmission, shift the transmission to
NEUTRAL.
Listen for relay clicks and gearmotor operation.
Hold the shift conditions for 20 seconds.
Is the 4X4 LOW indicator ON?
Yes
GO to A13.
No
GO to A12.
A12 ATTEMPT MECHANICAL ASSIST OF 4X4 LOW
ENGAGEMENT
CAUTION: Make sure there is a clear area
behind the vehicle before backing up.
Shift the transmission to REVERSE and back the
vehicle up 3 meters (10 feet) to relieve driveline
wind-up and stop.
Drive the vehicle forward for 3 meters (10 feet) and
stop.
Apply the brake pedal and hold.
For automatic transmission, shift to NEUTRAL.
Observe the 4X4 LOW indicator.
Is the 4X4 LOW indicator ON?
Yes
GO to A13.
No
RETRIEVE 4WD control module self-test DTCs. If a self-test DTC related to the concern is
retrieved, REFER to the 4WD Control Module Diagnostic Trouble Code (DTC) Index in this
section. If no DTC related to the concern is retrieved, GO to Pinpoint Test D.
A13 CHECK FOR MECHANICAL ENGAGEMENT OF
4X4 LOW
NOTE: Driveline wind-up and tire scuff is present in
both 4X4 and 4X4 LOW. However, vehicle speed is
severely limited in 4X4 LOW.
Execute tight turns on a hard surface.
Check for the presence of driveline wind-up, tire
scuff and reduced vehicle speed.
Is driveline wind-up, tire scuff and reduced
speed present?
Yes
GO to A14.
No
4X4 LOW did not mechanically engage. RETRIEVE 4WD control module self-test DTCs. If selftest DTC related to the concern is retrieved, REFER to the 4WD Control Module Diagnostic
Trouble Code (DTC) Index in this section. If no DTC related to the concern is retrieved, GO to
Pinpoint Test D.
A14 CHECK FOR CORRECT INDICATOR OPERATION
ON 4X4 LOW DISENGAGEMENT
While driving the vehicle forward above 8 km/h (5
mph), turn the MSS to 4X4 while observing the
indicators.
Turn the MSS to 4X4 LOW.
Stop the vehicle and apply the parking brake.
For automatic transmission, shift to PARK and
release the brake pedal.
Is the 4X4 LOW indicator ON?
Yes
GO to A15.
No
RETRIEVE 4WD control module self-test DTCs. If a self-test DTC related to the concern is
retrieved, REFER to the 4WD Control Module Diagnostic Trouble Code (DTC) Index in this
section. If no DTC related to the concern is retrieved, GO to Pinpoint Test D.
A15 CHECK THE 4X4 LOW INDICATOR
Turn the MSS to 4X4.
Apply and hold the brake pedal.
Is the 4X4 Low indicator ON?
Yes
GO to A16.
No
RETRIEVE 4WD control module self-test DTCs. If a self-test DTC related to the concern is
retrieved, REFER to the 4WD Control Module Diagnostic Trouble Code (DTC) Index in this
section. If no DTC related to the concern is retrieved, REFER to Section 413-01.
A16 CHECK FOR 4X4 LOW INDICATOR OFF IN 4X4
Press and hold the brake pedal.
For automatic transmission, shift the transmission to
Yes
GO to A18.
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NEUTRAL.
Listen for relay clicks and gearmotor operation.
Hold the shift conditions for 20 seconds. (The
system will use up to five cycles of shift attempts
trying to engage 4X4.)
Is the 4X4 LOW indicator OFF?
Page 6 of 18
No
GO to A17.
A17 ATTEMPT MECHANICAL ASSIST OF 4X4 LOW
DISENGAGEMENT
Drive the vehicle forward above 8 kmh (5 mph) for at
least five seconds.
Stop the vehicle.
Apply the brake pedal and hold.
For automatic transmission, shift to NEUTRAL.
Observe the 4X4 LOW indicator.
Is the 4X4 LOW indicator OFF?
Yes
GO to A18.
No
RETRIEVE 4WD control module self-test DTCs. If a self-test DTC related to the concern is
retrieved, REFER to the 4WD Control Module Diagnostic Trouble Code (DTC) Index in this
section. If no DTC related to the concern is retrieved, REFER to Section 413-01.
A18 CHECK FOR MECHANICAL 4X4 LOW
DISENGAGEMENT AND 4X4 ENGAGEMENT
Yes
GO to A19.
CAUTION: Make sure there is a clear area
behind the vehicle before backing up.
No
Shift the transmission to REVERSE and back the
4X4 LOW is mechanically bound or locked. REPAIR the transfer case as necessary. REFER to
vehicle up 3 meters (10 feet) to relieve driveline
Section 308-07B.
wind-up.
Stop the vehicle.
Drive the vehicle forward and execute tight turns on
a hard surface.
NOTE: Driveline wind-up and tire scuff are present in
both 4X4 and 4X4 LOW. However, vehicle speed is
severely limited in 4X4 LOW.
Verify the presence of driveline wind-up and tire
scuff. Also verify the increased vehicle speed from
when 4X4 LOW was engaged.
Did 4X4 engage and the vehicle speed increase?
Apply the brake.
A19 CHECK THE 4X4 TO 2WD SHIFT
Stop the vehicle.
Turn the MSS to 2WD and wait 20 seconds.
Listen for relay clicks and gearmotor operation.
Are the 4X4 and 4X4 LOW indicators OFF?
Yes
GO to A21.
No
GO to A20.
A20 ATTEMPT MECHANICAL ASSIST OF 4X4
DISENGAGEMENT
Drive the vehicle forward above 8 kmh (5 mph) for at
least 20 seconds.
Stop the vehicle.
Observe the 4X4 and 4X4 LOW indicators.
Are the 4X4 and 4X4 LOW indicators OFF?
Yes
GO to A21.
No
RETRIEVE 4WD control module self-test DTCs. If a self-test DTC related to the concern is
retrieved, REFER to the 4WD Control Module Diagnostic Trouble Code (DTC) Index in this
section. If no DTC related to the concern is retrieved, GO to A22 .
A21 VERIFY THE HUBLOCKS DISENGAGE
Raise and support the front tires off the ground until
they can be spun freely. Refer to Section 100-02.
Rotate the left front tire one revolution forward and
one revolution backward, while observing the left
front axle shaft and universal joint.
Rotate the right front tire one revolution forward and
one revolution backward, while observing the right
front axle shaft and universal joint.
Did either axle shaft rotate?
Yes
GO to Pinpoint Test E.
No
GO to A22.
A22 VERIFY THE TRANSFER CASE MECHANICALLY
DISENGAGED
Apply the parking brake.
Rotate the front driveshaft.
Does the front driveshaft turn?
Yes
GO to A23.
No
The transfer case did not disengage from 4X4. REPAIR the transfer case as necessary. REFER to
Section 308-07B.
A23 VERIFY THE HUBLOCKS WILL LOCK MANUALLY
Turn the MSS to 4X4.
Rotate the left front tire one revolution forward and
one revolution backward while observing the left
front axle shaft and universal joint.
Rotate the right front tire one revolution forward and
one revolution backward while observing the right
front axle shaft and universal joint.
Do both axles rotate?
Yes
GO to A24.
No
GO to Pinpoint Test E.
A24 VERIFY THE HUBLOCKS WILL UNLOCK
MANUALLY
Turn the MSS to 2WD.
Rotate the left front tire one revolution forward and
one revolution backward while observing the left
front axle shaft and universal joint.
Rotate the right front tire one revolution forward and
Yes
INSTALL a new hublock. REFER to Hublock in this section.
No
The transfer case is operating correctly. INSTRUCT the customer on correct system operation.
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Page 7 of 18
one revolution backward while observing the right
front axle shaft and universal joint.
Does either axle rotate?
Symptom Chart
Symptom Chart
Condition
The vehicle does not
operate correctly in A4WD
and 4WD HIGH modes
Possible Sources
GO to Pinpoint Test B.
Central junction
box (CJB) fuses:
115 (30A).
20 (30A).
4WD control
module.
4WD control
module
connectors.
Circuitry.
GO to Pinpoint Test C.
Central junction
box (CJB) fuses:
11 (10A).
115 (30A).
20 (30A).
Mode select
switch (MSS).
Gearmotor
encoder contact
plate A, B, C, or
D.
Gearmotor
encoder
assembly.
Circuitry.
4WD control
module.
Transfer case
internal
mechanism.
Transfer case
shift motor.
Digital TR sensor.
BPP switch.
IVD.
IWE solenoid.
4WABS control
module.
Instrument
cluster.
PCM.
GO to Pinpoint Test D.
Tire inflation
pressure.
Tire and wheel
size.
MAKE SURE that all tires and wheels are the same size and that the inflation
pressures are correct.
Tire tread wear.
CHECK tire tread wear to see if there is more than 0.15 mm (0.06 in) difference
in tread wear between front and rear. INTERCHANGE one front wheel and one
rear wheel. ROAD TEST again.
Internal
components.
OPERATE the vehicle in all transmission gears. If there is noise in the
transmission in NEUTRAL, or in some gears and not in others, REMOVE and
REPAIR the transmission. REFER to Section 307-01B. If there is noise in all
gears, DISASSEMBLE the transfer case. REFER to Section 308-07B. CHECK
the planetary gears, bearings, upper and lower drive sprockets and drive chain
for damage. INSTALL new parts as necessary.
Fluid level.
FILL with automatic transmission fluid. REFER to Section 308-07B.
No communication with the
4WD control module
The vehicle does not shift
between 4X4AUTO/4WD
HIGH and 4WD LOW
modes correctly
The transfer case makes
noise
Action
Central junction
box (CJB) fuses:
11 (10A).
115 (30A).
20 (30A).
Mode select
switch (MSS).
Transfer case
shaft speed
sensors.
Transfer case
electric clutch.
4WD control
module.
Powertrain control
module (PCM).
IVD.
IWE solenoid.
Circuitry.
Pinpoint Tests
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Page 8 of 18
PINPOINT TEST B: THE VEHICLE DOES NOT OPERATE CORRECTLY IN A4WD AND 4WD HIGH MODES
Test Step
Result / Action to Take
B1 CHECK INDICATOR PROVE-OUT
Ignition OFF.
Start the vehicle while observing the 4WD indicators for prove
out.
Did indicators prove out?
Yes
GO to B3.
No
GO to B2.
B2 CHECK FOUR-WHEEL DRIVE (4WD) CONTROL MODULE
COMMUNICATION
Ignition ON.
Connect the scan tool.
Retrieve the 4WD control module self-test DTCs.
Did the 4WD control module respond?
Yes
REPAIR the instrument cluster as necessary. REFER to Section 413-01.
No
GO to Pinpoint Test C.
B3 CHECK FOR A4WD SYSTEM ERROR
Turn the vehicle off and restart the vehicle.
Is the 4WD HIGH indicator flashing several times?
Yes
GO to B13.
No
GO to B4.
B4 CHECK FOR THE PRESENCE OF 4WD
Select 4 HIGH on the mode select switch (MSS).
Execute tight turns on a hard surface.
Check for the presence of driveline windup and tire scuff.
Are driveline windup and tire scuff present with 4X4 HIGH
indicator on?
Yes
GO to B5.
No
GO to B21.
B5 REVIEW THE FOUR-WHEEL DRIVE (4WD) CONTROL
DIAGNOSTIC TROUBLE CODES
CARRY OUT the 4WD control module self-test.
Are any DTCs retrieved?
Yes
If DTC B1317 or B1318 is retrieved, GO to Pinpoint Test C. If DTC C1728, C1729,
P1849, P1853, P1857, P1861, P1867 or P1891 is retrieved, GO to Pinpoint Test D. If
DTC B2105 or B2106 or both are retrieved,GO to B19 . If DTC C1979 or C1980 or
both is retrieved, GO to B22 . If DTC P1824, P1826 or P1827 is retrieved, GO to B14 .
No
GO to B6.
B6 CHECK THE 4WD MODE SELECT SWITCH IN THE 2WD
POSITION (MONITOR THE PID 4WD_SW)
Yes
GO to B7.
Monitor the PID 4WD_SW.
Select 2WD on the 4WD MSS.
Does the PID 4WD_SW indicate 2WD?
No
GO to B10.
B7 CHECK THE 4WD MODE SELECT SWITCH IN THE A4WD
POSITION (MONITOR THE PID 4WD_SW)
Monitor the PID 4WD_SW.
Select A4WD on the 4WD MSS.
Does the PID 4WD_SW indicate A4WD?
Yes
GO to B8.
No
GO to B10.
B8 CHECK THE 4WD MODE SELECT SWITCH IN THE 4WD HIGH
POSITION (MONITOR THE PID 4WD_SW)
Monitor the PID 4WD_SW.
Select 4WD HIGH on the 4WD MSS.
Does the PID 4WD_SW indicate 4WD HIGH?
Yes
GO to B9.
No
GO to B10.
B9 CHECK THE 4WD MODE SELECT SWITCH IN THE 4WD LOW
POSITION (MONITOR THE PID 4WD_SW)
Monitor the PID 4WD_SW.
Select 4WD LOW on the 4WD MSS.
Does the PID 4WD_SW indicate 4WD LOW?
Yes
GO to B12.
No
GO to B10.
B10 CHECK THE MODE SELECT (MSS) SWITCH
Ignition OFF.
Disconnect: Mode Select Switch (MSS) C284.
Rotate the MSS to the A4WD, 4H, and 4L positions.
Measure the resistance between MSS terminals 2 and 3 while
rotating the switch through all positions; refer to the following
chart.
Yes
GO to B11.
No
INSTALL a new MSS. CLEAR the DTCs. TEST the system for normal operation.
Mode Select Switch (MSS) Position Resistance Range
A4WD
264.33 - 269.67
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4WD HIGH
128.7 - 131.3
4WD LOW
61.38 - 62.62
2WD HIGH
616.9 - 623.1
Page 9 of 18
Are the resistances within specification?
B11 CHECK CIRCUIT 682 (DB) FOR AN OPEN
Ignition OFF.
Disconnect: Mode Select Switch C284.
Disconnect: 4WD Module C3184b.
Measure the resistance between MSS C284 pin 2, circuit 682
(DB) and 4WD control module C4184b pin 10, circuit 682 (DB).
Yes
GO to B12.
No
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
Is the resistance less than 5 ohms?
B12 CHECK CIRCUIT 780 (DB) FOR A SHORT TO VOLTAGE
Ignition ON.
Measure the voltage between 4WD control module C3184b, pin
16, circuit 780 (DB) and ground.
Yes
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
No
GO to B13.
Is any voltage present?
B13 CHECK CIRCUIT 780 (DB) FOR A SHORT TO GROUND
Ignition OFF.
Measure the resistance between 4WD control module C3184b,
pin 16, circuit 780 (DB) and ground.
Yes
GO to B14.
No
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
Is the resistance greater than 10,000 ohms?
B14 CHECK THE ELECTRIC CLUTCH—ENERGIZED
Connect: 4WD Control Module C3184a.
Connect: 4WD Control Module C3184b.
Ignition ON.
Select NEUTRAL.
Select 4WD HIGH on the MSS.
Raise and support the vehicle; refer to Section 100-02.
Connect the scan tool.
Trigger the electric clutch control output command
(CLUTCHSOL). Set the command to 100 percent.
Rotate the front driveshaft.
Yes
GO to B15.
No
GO to B16.
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Page 10 of 18
Does the front driveshaft lock to the rear?
B15 CHECK THE ELECTRIC CLUTCH—NOT ENERGIZED
Connect the scan tool.
Trigger the electric clutch control output command
(CLUTCHSOL). Set the command to zero percent.
Rotate the front driveshaft.
Does the front driveshaft lock to the rear?
Yes
GO to B17.
No
GO to Section 206-09.
B16 CHECK THE VOLTAGE TO THE ELECTRIC CLUTCH—
ENERGIZED
Ignition OFF.
Disconnect: Transfer Case C350.
Ignition ON.
Trigger the electric clutch control output command
(CLUTCHSOL). Set the command to 100 percent.
Measure the voltage between transfer case C350 pin 8, circuit
779 (BN) and ground.
Yes
INSTALL a new electric clutch. REFER to Section 308-07B. CLEAR the DTCs. TEST
the system for normal operation.
No
GO to B19.
Is the voltage greater than 10 volts?
B17 CHECK THE VOLTAGE TO THE ELECTRIC CLUTCH—NOT
ENERGIZED
Ignition OFF.
Disconnect: Transfer Case C350.
Ignition ON.
Measure the voltage between transfer case C350 Pin 8, circuit
779 (BN) and ground.
Yes
INSTALL a new electric clutch. REFER to Section 308-07B. CLEAR the DTCs. TEST
the system for normal operation.
No
GO to B18.
Is the voltage zero volts?
B18 CHECK CIRCUIT 779 (BN) FOR SHORT TO VOLTAGE
Ignition OFF.
Disconnect: 4WD Control Module C3184a.
Ignition ON.
Measure the voltage between 4WD control module C3184a pin
17, circuit 779 (BN), harness side and ground.
Yes
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
No
GO to B19.
Is any voltage present?
B19 CHECK CIRCUIT 779 (BN) FOR AN OPEN
Ignition OFF.
Measure the resistance between transfer case C350 pin 8,
circuit 779 (BN) and 4WD control module C3184a pin 17, circuit
779 (BN).
Yes
GO to B20.
No
REPAIR the circuit. CLEAR the DTCs. TEST the system for normal operation.
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Is the resistance less than 5 ohms?
B20 CHECK THE THROTTLE POSITION INPUT—MONITOR THE
4WD PID TPI
Ignition ON.
Monitor the PID: TPI while pressing and releasing the
accelerator pedal.
Does the PID: TPI increase when the accelerator pedal is
pressed and decrease when the accelerator pedal is
released?
Yes
DISCONNECT 4WD control module connector C3184b and the PCM connector
C1752. INSPECT circuit 1498 (PK/OG) for signs of corrosion or damage. If OK,
RECONNECT the connectors making sure they seat correctly. CLEAR the DTCs.
TEST the system for normal operation.
No
GO to B21.
B21 CHECK CIRCUIT 1498 (PK/OG) FOR A SHORT TO VOLTAGE
Ignition ON.
Measure the voltage between 4WD control module C3184b pin
14, circuit 1498 (PK/OG), harness side and ground.
Yes
REPAIR the circuit. CLEAR the DTCs. TEST the system for normal operation.
No
REFER to Powertrain Control/Emissions Diagnosis (PC/ED) manual for diagnosis and
testing of the PCM.
Is any voltage indicated?
B22 CHECK CIRCUIT 474 (OG/LG) FOR OPEN
Disconnect: IWE Solenoid C1157.
Measure the voltage between IWE solenoid C1157 pin 1, circuit
474 (OG/LG) and ground.
Yes
GO to B23.
No
REPAIR the circuit. CLEAR the DTCs. TEST the system for normal operation.
Is the voltage greater than 10 volts?
B23 CHECK CIRCUIT 605 (RD) FOR SHORT TO GROUND
Measure the resistance between IWE solenoid C1157 pin 2,
circuit 605 (RD) and ground.
Yes
GO to B24.
No
REPAIR the circuit. CLEAR the DTCs. TEST the system for normal operation.
Is the resistance greater than 10,000 ohms?
B24 CHECK CIRCUIT 605 (RD) FOR OPEN
Disconnect: 4WD Control Module C3184b.
Measure the resistance between IWE solenoid C1157 pin 2,
circuit 605 (RD) and 4WD control module C3184b pin 12, circuit
605 (RD).
Yes
GO to B25.
No
REPAIR the circuit. CLEAR the DTCs. TEST the system for normal operation.
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Page 12 of 18
Is the resistance less than 5 ohms?
B25 CHECK IWE SOLENOID
Carry out the IWE solenoid component test.
Refer to Wiring Diagrams Cell 149 for component testing.
Did the IWE solenoid pass the component tests?
Yes
GO to B26.
No
INSTALL a new IWE solenoid. CLEAR the DTCs. TEST the system for normal
operation.
B26 CHECK FOR CORRECT 4WD CONTROL MODULE
OPERATION
Disconnect all 4WD control module connectors.
Check for:
corrosion
pushed-out pins
Connect all 4WD control module connectors and make sure they
seat correctly.
Operate the system and verify the concern is still present.
Is the concern still present?
Yes
INSTALL a new 4WD control module. CLEAR the DTCs. REPEAT the self-test.
No
The system is operating correctly at this time. Concern may have been caused by a
loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.
PINPOINT TEST C: NO COMMUNICATION WITH THE FOUR-WHEEL DRIVE (4WD) CONTROL MODULE
Test Step
Result / Action to Take
C1 CHECK POWER TO 4WD CONTROL MODULE
Ignition OFF.
Disconnect: 4WD Control Module C3184b.
Ignition ON.
Measure the voltage between 4WD control module and ground. Refer to the following chart:
4WD Control Module Pin
Circuit
C3184b pin 8
1524 (DB)
C3184b pin 17
704 (DG/LG)
Yes
GO to C2.
No
REPAIR the circuit(s) in question. TEST the system for
normal operation.
Are all of the voltage measurements greater than 10 volts?
C2 CHECK 4WD CONTROL MODULE GROUND CIRCUITS
Ignition OFF.
Disconnect: 4WD Control Module C3184a.
Disconnect: 4WD Control Module C3184b.
Measure the resistance between 4WD control module C3184a, pin 1, circuit 57 (BK), harness
side and ground; and between 4WD control module C3184b, pin 2, circuit 875 (BK/LB), harness
side and ground.
Yes
GO to C3.
No
REPAIR the circuit. TEST the system for normal
operation.
Are both resistance less than 5 ohms?
C3 CHECK FOR CORRECT 4WD CONTROL MODULE OPERATION
Disconnect all 4WD control module connectors (C3184a and C3184b), and the transfer case
Yes
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Page 13 of 18
connector (C350).
Check for:
corrosion
pushed-out pins
Connect all 4WD control module connectors and the transfer case connector and make sure
they seat correctly.
Operate the system and verify the concern is still present.
Is the concern still present?
INSTALL a new 4WD control module. CLEAR the
DTCs. REPEAT the self-test.
No
The system is operating correctly at this time. Concern
may have been caused by a loose or corroded
connector. CLEAR the DTCs. REPEAT the self-test.
PINPOINT TEST D: THE VEHICLE DOES NOT SHIFT BETWEEN AUTO/4WD HIGH AND 4WD LOW MODES CORRECTLY
Test Step
Result / Action to Take
D1 REVIEW THE FOUR-WHEEL DRIVE (4WD) CONTROL DIAGNOSTIC TROUBLE CODES
Connect the scan tool.
CARRY OUT the 4WD control module self-test.
Are any DTCs retrieved?
Yes
If DTC B2105, B2106, C1979 or C1980 are retrieved, GO to
Pinpoint Test B. If DTC P1812 is retrieved, GO to D5 . If DTC
P1849, P1853, P1857, P1861 or P1867 are retrieved, GO to
D10 . If DTC U1900, U1950, U2023, U2306 or U2226 is
retrieved, REFER to Section 418-00. For all other DTCs, GO
to D2 .
No
GO to D2.
D2 CHECK THE DIGITAL TRANSMISSION RANGE (TR) SENSOR
CARRY OUT the instrument cluster module self-test.
Are any DTCs retrieved?
Yes
Section 413-01.
No
GO to D3.
D3 CHECK BRAKE PEDAL SWITCH PID
Monitor the ABS module brake input switch status PID.
Step on the brake pedal.
Does the brake input switch status PID indicate active?
Yes
GO to D4.
No
REFER to Section 206-09.
D4 CHECK WHEEL SPEED SENSOR INPUTS
Monitor the ABS module wheel speed sensor inputs.
Do the wheel speed sensor inputs indicate 0 kph (0 mph)?
Yes
GO to D5.
No
REFER to Section 206-09.
D5 CHECK THE MODE SELECT SWITCH (MSS)—MONITOR THE 4WD CONTROL
MODULE PID 4WD_SW
Ignition ON.
Monitor the 4WD control module PID: 4WD_SW while selecting each of the positions on
the mode select switch (MSS).
Do the 4WD control module PID values agree with the MSS positions?
Yes
GO to D7.
No
GO to D6.
D6 CHECK THE MSS — ALL POSITIONS
Yes
Disconnect: MSS C284.
Measure the resistance between MSS terminals 2 and 3 while rotating the switch through GO to D7.
all positions. Refer to the following chart:
No
INSTALL a new MSS. REFER to Mode Select Switch (MSS)
MSS Position Resistance
in this section. CLEAR the DTCs. REPEAT the self-test.
A4WD
264.33 - 269.67
4WD HIGH
128.7 - 131.3
4WD LOW
61.38 - 62.62
2WD HIGH
616.9 - 623.1
Are all the resistances within the specified values?
D7 CHECK CIRCUITS 682 (DB) AND 780 (DB) FOR A SHORT TO POWER
Disconnect: 4WD Control Module Connector C3184b.
Ignition ON.
Measure the voltage between 4WD control module connector C3184b pin 10, circuit 682
(DB) and ground.
Yes
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT
the self-test.
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Measure the voltage between 4WD control module connector C3184b pin 16, circuit 780
(DB) and ground.
Is voltage present on either pin?
Page 14 of 18
No
GO to D8.
D8 CHECK CIRCUITS 682 (DB) AND 780 (DB) FOR AN OPEN
Ignition OFF.
Measure the resistance between 4WD control module C3184b pin 10, and MSS C284 pin
2, circuit 682 (DB).
Measure the resistance between 4WD control module C3184b pin 16 and MSS C284 pin
3, circuit 780 (DB).
Yes
GO to D9.
No
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT
the self-test.
Are the resistance less than 5 ohms?
D9 CHECK FOR CORRECT 4WD CONTROL MODULE OPERATION
Ignition OFF.
Disconnect: Disconnect: 4WD Control Module Connector (C3184a) and the Transfer
Case Connector (C350)..
Check for:
corrosion
pushed-out pins
Connect both 4WD control module connectors (C3184a and C3184b) and the transfer
case connector (C350), making sure they seat correctly.
Operate the system and verify the concern is still present.
Is the concern still present?
Yes
GO to D10.
No
The system is operating correctly at this time. Concern may
have been caused by a loose or corroded connector. CLEAR
the DTCs. REPEAT the self-test.
D10 CHECK THE CONTACT PLATE ENCODER SWITCH
Place the transmission range selector lever in NEUTRAL (for manual transmission, press
and hold the clutch pedal).
Press and hold the brake pedal.
Monitor mode select switch (MSS) PID.
Monitor the contact plate PIDs: PLATE_A, PLATE_B, PLATE _C and PLATE_D.
NOTE: The contact plate PIDs can only be read for approximately two seconds. To
continue reading, cycle the MSS again.
Cycle the MSS to A4WD and 4WD LOW two times.
Compare the contact plate PID values for each shift position selected by the MSS. Refer
to the following chart:
Yes
GO to D17.
No
GO to D11.
Plate PID MSS PID A4WD MSS PID 4WD LOW
PLATE_A
CLOSED
OPEN
PLATE_B
OPEN
CLOSED
PLATE_C
CLOSED
OPEN
PLATE_D
CLOSED
CLOSED
Do the contact plate PID values agree with the MSS PIDs?
D11 CHECK CIRCUIT 762 (YE/WH), CIRCUIT 763 (OG/WH), CIRCUIT 764 (BN/WH),
CIRCUIT 770 (WH), AND CIRCUIT 771 (VT/YE) FOR A SHORT TO VOLTAGE
Ignition OFF.
Disconnect: 4WD Control Module C3184a.
Ignition ON.
Measure the voltage between the following circuits at the 4WD control module connector
pins and ground:
Circuit
4WD Control Module Connector and Pins
762 (YE/WH)
C3184a pin 3
763 (OG/WH)
C3184a pin 4
764 (BN/WH)
C3184a pin 5
770 (WH)
C3184a pin 6
771 (VT/YE)
C3184a pin 7
Yes
REPAIR the circuit(s) in question. CLEAR the DTCs. REPEAT
the self-test.
No
GO to D12.
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Is any voltage present?
D12 CHECK CIRCUIT 762 (YE/WH), CIRCUIT 763 (OG/WH), CIRCUIT 764 (BN/WH),
CIRCUIT 770 (WH), AND CIRCUIT 771 (VT/YE) FOR A SHORT TO GROUND
Ignition OFF.
Disconnect: Transfer Case C350.
Measure the resistance between the following circuits at the 4WD control module
connector pins and ground:
Circuit
4WD Control Module Connector and Pins
762 (YE/WH)
C3184a pin 3
763 (OG/WH)
C3184a pin 4
764 (BN/WH)
C3184a pin 5
770 (WH)
C3184a pin 6
771 (VT/YE)
C3184a pin 7
Yes
GO to D13.
No
REPAIR the circuit(s) in question. CLEAR the DTCs. REPEAT
the self-test.
Are the resistances all over 10,000 ohms?
D13 CHECK CIRCUIT 762 (YE/WH), CIRCUIT 763 (OG/WH), CIRCUIT 764 (BN/WH),
CIRCUIT 770 (WH), AND CIRCUIT 771 (VT/YE) FOR AN OPEN
Measure the resistance of the following circuits at the 4WD control module connector
pins and transfer case connector pins shown.
Circuit
4WD Control Module Connector and Transfer Case Connector and
Pins
Pins
762
(YE/WH)
C3184a pin 3
C350 pin 6
763
(OG/WH)
C3184a pin 4
C350 pin 3
764
(BN/WH)
C3184a pin 5
C350 pin 2
770 (WH)
C3184a pin 6
C350 pin 1
771 (VT/YE)
C3184a pin 7
C350 pin 5
Yes
GO to D14.
No
REPAIR the circuit or circuit(s) in question. CLEAR the DTCs.
REPEAT the self-test.
Are all the resistances less than 5 ohms?
D14 CHECK CIRCUIT 777 (YE) AND CIRCUIT 778 (OG) FOR A SHORT TO VOLTAGE
Ignition ON.
Measure the voltage between 4WD control module C3184a, pin 9, circuit 777 (YE),
harness side and ground; and between 4WD control module C3184a, pin 2, circuit 778
(OG), harness side and ground.
Yes
REPAIR the circuit(s). CLEAR the DTCs. REPEAT the selftest.
No
GO to D15.
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Is any voltage present?
D15 CHECK CIRCUIT 777 (YE) AND CIRCUIT 778 (OG) FOR AN OPEN
Measure the resistance between 4WD control module C3184a, pin 9, circuit 777 (YE),
harness side and transfer case C350, pin 4, circuit 777 (YE), harness side; and between
4WD control module C3184a, pin 2, circuit 778 (OG), harness side and transfer case
C350, pin 7, circuit 778 (OG), harness side.
Yes
GO to D16.
No
REPAIR the suspect circuit. CLEAR the DTCs. REPEAT the
self-test.
Are the resistances less than 5 ohms?
D16 CHECK CIRCUIT 777 (YE) AND CIRCUIT 778 (OG) FOR A SHORT TO GROUND
Measure the resistance between 4WD control module C3184a, pin 9, circuit 777 (YE),
harness side and ground; and between 4WD control module C3184a, pin 2, circuit 778
(OG), harness side and ground.
Yes
GO to D17.
No
REPAIR the suspect circuit. CLEAR the DTCs. REPEAT the
self-test.
Are the resistances more than 10,000 ohms?
D17 CHECK THE TRANSFER CASE
Ignition OFF.
Release the parking brake.
Using a wrench, manually shift the transfer case sector shaft to the full clockwise (AUTO)
direction while turning the rear driveshaft.
Apply the parking brake.
Rotate the front driveshaft.
Does the front driveshaft turn?
Yes
GO to D18.
No
REPAIR the transfer case as necessary. REFER to Section
308-07B. TEST the system for normal operation.
D18 CHECK THE SECTOR SHAFT TURNING EFFORT
NOTE: The transfer case has three detented shift positions. The full clockwise position is Yes
AUTO and the full counterclockwise position is 4WD LOW. Normal operation should not REPAIR the transfer case as necessary. REFER to Section
308-07B. TEST the system for normal operation.
take more than 45 Nm (33 lb-ft) to manually shift the transfer case.
Release the parking brake.
Using a torque wrench, manually shift the transfer case sector shaft in a
counterclockwise direction to the 4WD HIGH detent position while rotating the rear
driveshaft.
Did the torque required to shift exceed 45 Nm (33 lb-ft)?
No
GO to D19.
D19 CHECK THE TRANSFER CASE SHIFT TO 4WD HIGH AND 4WD LOW
Yes
REPAIR the transfer case as necessary. REFER to Section
308-07B.
Apply the parking brake.
Rotate the front driveshaft.
Does the front driveshaft rotate?
No
INSTALL a new gearmotor encoder assembly. REFER to
Gearmotor Encoder Assembly in this section. CLEAR the
DTCs. REPEAT the self-test. If still inoperative, INSTALL a
new 4WD control module. REFER to Four-Wheel Drive (4WD)
Control Module in this section. CLEAR the DTCs. REPEAT
the self-test.
PINPOINT TEST E: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY
Test Step
Result / Action to Take
E1 CHECK THE HUBLOCKS DISENGAGEMENT
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Lift and support the vehicle off the ground until the front tires can be spun freely. Refer to
Section 100-02.
NOTE: The engine is required to be at idle during the following steps to supply the vacuum
required for the hublocks to engage and disengage.
Yes
GO to E2.
No
GO to Pinpoint Test D.
Start engine and allow to idle.
Place the shift selector into 2H mode.
Spin the tires.
Are the hub locks engaged?
E2 CHECK FOR GROSS VACUUM LEAK
Yes
REPAIR or INSTALL a new vacuum supply hose or
vacuum reservoir as necessary. REFER to Section 41200.
Set the heater control to FLOOR.
Check heat output at defroster vents.
Is the heater mode selector stuck at DEFROST?
No
GO to E3.
E3 CHECK FOR VACUUM LEAK IN FRONT AXLE HUB LOCK SYSTEM
Disconnect the vacuum line at the IWE solenoid (located on the firewall behind the battery).
Yes
GO to E4.
No
GO to E7.
Connect the vacuum pump to the vacuum supply line.
Apply a vacuum of 20 inches of mercury to the hublock vacuum for 30 seconds.
Is a vacuum leak greater than 25 mm (1 in) Hg/minutes indicated?
E4 CHECK FOR VACUUM LEAK IN RIGHT FRONT AXLE HUBLOCK
Yes
GO to E5.
Disconnect and plug the vacuum line at the RF hublock.
Apply a vacuum of 20 inches of mercury directly to RF hublock assembly.
Monitor the hublock vacuum for 30 seconds.
Does the RF hublock leak down at a rate less than 1 inHg/minute?
No
INSTALL a new hublock. REFER to Section 205-03.
E5 CHECK FOR VACUUM LEAK IN LEFT FRONT AXLE HUBLOCK
Yes
GO to E6.
Disconnect and plug the vacuum line at the LF hublock.
Apply a vacuum of 20 inches of mercury directly to the LF hublock.
Monitor the system vacuum for 30 seconds.
Does the LF hublock leak down at a rate less than 1 inHg/minute?
No
INSTALL a new hublock. REFER to Section 205-03.
E6 CHECK FOR VACUUM LEAK IN VACUUM LINES
Connect the vacuum pump to the vacuum supply line. Cap off the vacuum delivery line at both
actuators.
Apply a vacuum of 20 inches of mercury to the hublock vacuum system.
Monitor the system vacuum for 30 seconds.
Is a vacuum leak greater than 1 inHg/minute indicated?
Yes
REPAIR or INSTALL a new vacuum supply hose or
tube as necessary.
No
GO to E7.
E7 CHECK FOR CORRECT FOUR-WHEEL DRIVE CONTROL MODULE OPERATION
Ignition OFF.
Disconnect all four-wheel drive control module connectors (C3184a and C3184b) and the
transfer case connector (C350).
Check for:
corrosion
pushed-out pins
Connect all four-wheel drive control module connectors (C3184a and C3184b) and the transfer
case connector (C350), and make sure that they seat correctly.
Operate the system and verify the concern is still present.
Is the concern still present?
Yes
INSTALL a new four-wheel drive control module.
No
The system is operating correctly at this time. Concern
may have been caused by a loose or corroded
connector.
PINPOINT TEST F: DTCS C1979/C1980 — IWE SOLENOID CIRCUIT FAILURE/IWE SOLENOID SHORT TO BATTERY
Test Step
Result / Action to Take
F1 CHECK CIRCUIT 605 (RD) FOR SHORT TO BATTERY
Disconnect: IWE Solenoid C1157.
Disconnect: Four Wheel Drive (4WD) Control Module C3184b.
Measure the voltage between IWE solenoid C1157 pin 2, circuit 605 (RD) harness
side and ground.
Is voltage present?
Yes
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
No
IF DTC C1979, GO to F2 .
If DTC C1980, INSTALL a new four wheel drive (4WD) control
module. REFER to Four Wheel Drive (4WD) Control Module in
this section. REPEAT the self-test.
F2 CHECK CIRCUIT 605 (RD) FOR SHORT TO GROUND
Measure the resistance between IWE solenoid C1157 pin 2, circuit 605 (RD) harness
Yes
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2003 Expedition/Navigator Workshop Manual
side and ground.
Is the resistance greater than 10,000 ohms?
Page 18 of 18
GO to F3.
No
REPAIR the circuit. CLEAR the DTC. REPEAT the self-test.
F3 CHECK CIRCUIT 605 (RD) FOR AN OPEN (TO MODULE)
Measure the resistance between IWE solenoid C1157 pin 2 harness side and four
wheel drive control module C3184b pin 12 harness side circuit 605 (RD).
Is the resistance less than 5 ohms?
Yes
GO to F4.
No
REPAIR the circuit. CLEAR the DTC. REPEAT the self-test.
F4 CHECK THE IWE SOLENOID RESISTANCE
Measure the resistance between IWE solenoid C1157-1 and C1157-2 component
side.
Yes
GO to F5.
No
INSTALL a new IWE solenoid. CLEAR the DTCs. REPEAT the
self-test.
Is the resistance between 68 and 78 ohms?
F5 CHECK CIRCUIT 605 (RD) FOR AN OPEN (TO CJB)
Remove CJB fuse 11 (10A).
Measure the resistance between fuse cavity 11, output side and IWE solenoid C1157
pin 1 harness side, circuit 605 (RD).
Is the resistance less than 5 ohms?
Yes
INSTALL a new IWE solenoid. CLEAR the DTC. REPEAT the
self-test.
No
REPAIR the circuit. CLEAR the DTC. REPEAT the self-test.
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