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Home >> Ford >> 2020 >> Expedition SSV, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 1 (Four-Wheel Drive Systems) >> Diagnosis And Testing >> Four-Wheel Drive Systems - Vehicles With: 2-Speed Torque On Demand Transfer Case >> Pinpoint Tests >> Pinpoint Test A : Four-Wheel Drive (4WD) System Functional Test
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Pinpoint Test A : Four-Wheel Drive (4WD) System Functional Test

WARNING: This page is about a different variant/trim than selected.
  1. Normal Operation and Fault Conditions 

    The following parameters may be monitored in datalogger during this test:

    ATCM TCCM
    LAST_DIR_CLCK_RT 4x4_SW
    LAST_DIR_CNTR_LEFT IWE_OUT_ENGAGED #

    Locator views for the vacuum lines and vacuum reservoir are located in Description and Operation. REFER to: Four-Wheel Drive Systems - System Operation and Component Description for schematic and connector information.

    The four wheel drive system functional test will isolate and test each sub-system to determine if the subsystem is functioning properly. If a fault is found, additional testing of the suspect subsystem will be required.

    When operating in 2H mode, the transfer case clutch is de-energized and both IWE are unlocked. The TCCM may engage the IWE in 2H mode to speed warm up of the front axle fluid. The transfer case has certain amount of clutch drag which can cause the front driveshaft to spin in 2H mode.

    When operating in 4WD modes both IWE are locked. In 4A, the TCCM will apply the clutch when needed to control wheel slip.

    When operating in 4H and 4L modes both IWEs and the transfer case are locked. The vehicle will bind in turns in 4H and 4L modes.

    DTC Fault Trigger Conditions 

    DTC Description Fault Trigger Condition
    TCCM C1979:00 IWE Solenoid Circuit Failure: No Sub Type Information This DTC sets when the TCCM detects there is a possible mechanical fault present with the IWE system based on wheel speed message data. When the DTC is present IWE solenoid output shall continue to operate normally.

    Possible Sources 

    • 4WD system and/or related components

  2. NOTE: 4X4 High and 4X4 Low are not intended for driving on hard/dry surfaces. Using these modes while driving on these surfaces may produce noises like intermittent clunking, but does not damage driveline components.

  3. A1 CHECK THE MODULES FOR ON DEMAND DTC (DIAGNOSTIC TROUBLE CODE)

    • Ignition ON.

    • Gear Selector in Park.

    • Enter the following diagnostic mode:

      • TCCM KOEO Self-test.

      • ATCM KOEO Self-test.

    Is any DTC retrieved? 

    Yes  REFER to DTC Chart(s) .
    No  GO to  A2

  4. A2 CHECK ROTARY SWITCH

    NOTE: For vehicles not equipped with a rotary drive mode switch, go to  A3.

    • Gear Selector in Park.

    • Start Engine.

    • Enter the Diagnostic Mode: Datalogger ATCM.

    • Monitor the PID LAST_DIR_CLCK_RT and LAST_DIR_CNTR_LEFT while rotating the ATCM knob clockwise and counterclockwise

    Do the PID update correctly indicating the last direction the rotary knob was rotated? 

    Yes  GO to  A3
    No  INSTALL a new ATCM, REFER to: All Terrain Control Module (ATCM) .

  5. A3 CHECK SWITCH INPUT TO THE TCCM (TRANSFER CASE CONTROL MODULE) IN 2H

    • NORMAL drive mode.

    • Gear Selector in Park.

    • Engine running.

    • Enter the Diagnostic Mode: Datalogger >> TCCM.

    • Monitor the PID 4x4_SW.

    Does the 4x4_SW display Two Wheel Drive? 

    Yes  The TCCM recognizes a valid input from the ATCM. GO to  A4
    No  INSTALL a new ATCM. REFER to: All Terrain Control Module (ATCM) .

  6. A4 CHECK THE IWE DISENGAGEMENT

    NOTE: The TCCM may command the IWE to engage during 2H operation to warm up the front axle.

    • With the vehicle in NEUTRAL, position it on a hoist. Raise the vehicle until all 4 wheels are off the ground. REFER to: Jacking and Lifting .

    • Engine running.

      • The engine must idle for up to 5 minutes for the vacuum on demand system to build up the vacuum required for the IWE to disengage.

      • Allow engine to idle for 5 minutes

    • Gear selector in Neutral.

    • NORMAL drive mode.

    • Enter the following diagnostic mode: Datalogger >> TCCM

    • Command IWE_OUT_ENGAGED # to No (False)

    • Rotate the LH front tire one revolution forward and one revolution backward while observing the LH front halfshaft.

    • Rotate the RH front tire one revolution forward and one revolution backward while observing the RH front halfshaft.

    Did both front halfshafts remain stationary? 

    Yes  End Output State Control. GO to  A5
    No  End Output State Control. GO to Pinpoint Test E 

  7. A5 CHECK THE IWE ENGAGEMENT

    • Vehicle on hoist with all 4 wheels off the ground.

    • Engine running.

    • Gear selector in Neutral.

    • SAND drive mode.

    • Rotate the LH front tire one revolution forward and one revolution backward while observing the LH front halfshaft.

    • Rotate the RH front tire one revolution forward and one revolution backward while observing the RH front halfshaft.

    Did both front halfshafts rotate? 

    Yes  The front axle is operating properly at this time. GO to  A6
    No  GO to Pinpoint Test E 

  8. A6 CHECK TORQUE ON DEMAND CLUTCH OPERATION

    • SAND drive mode.

    • Enter the following diagnostic mode: Datalogger >> TCCM.

    • Command 4WD_CLTCH_OUT # to 70-80%.

    Is wind-up / vehicle bind present? 

    Yes  The TOD clutch is transmitting torque as expected. GO to  A7
    No  The TOD clutch is slipping / not transferring torque. CHECK the transfer case. REFER to: Transfer Case - Vehicles With: 2-Speed Torque On Demand Transfer Case .

  9. A7 CHECK RANGE FORK OPERATION

    • Engine running.

    • Gear selector in NEUTRAL, vehicle stopped.

    • Select 4L on the ATCM (Ford) or SLOW CLIMB drive mode (Lincoln).

    Does 4L indicator illuminate on the IPC? 

    Yes  The shift motor moved to engage 4L. GO to  A8
    No  GO to Pinpoint Test G 

  10. A8 CHECK 4L OPERATION

    • Select 4L on the ATCM (Ford) or SLOW CLIMB drive mode (Lincoln).

    • Drive the vehicle up to 10 mph.

    Did the transfer case engage LOW range? 

    Yes  GO to  A9
    No  The shift motor moved to engage 4L, but the transfer case did not provide a reduced gear ratio. CHECK the transfer case. REFER to: Transfer Case - Vehicles With: 2-Speed Torque On Demand Transfer Case .

  11. A9 CHECK FOR WIND-UP IN 2H MODE WITH IWE (INTEGRATED WHEEL END) ENGAGED

    • NORMAL drive mode.

    • Enter the following diagnostic mode: datalogger >> TCCM.

    • Command IWE_OUT_ENGAGED # to Yes (True).

    • 4 Drive the vehicle on a dry, hard surface while full lock turns.

    Is wind-up / vehicle bind present? 

    Yes  Exit Output State Control. The transfer case is unable to disengage 4x4. CHECK the transfer case. REFER to: Transfer Case - Vehicles With: 2-Speed Torque On Demand Transfer Case .
    No  Exit Output State Control. The 4WD system is operating as designed
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