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Home >> Ford >> 2000 >> Excursion 7.3 F, 4WD >> Repair and Diagnosis >> Transmission >> Transfer Case >> Four-Wheel Drive Systems (ESOF) - Excursion & F250-F550 Super Duty >> Diagnostic Tests >> Test B: Vehicle Does Not Shift Between 4WD High & 4WD Low Properly

Test B: Vehicle Does Not Shift Between 4WD High & 4WD Low Properly

  1. Check Ignition States; Monitor GEM PID IGN_GEM

    Turn ignition off. Connect NGS tester. Depress clutch pedal, if applicable. Monitor GEM PID Ignition Switch Status (IGN_GEM) while turning ignition switch through START, RUN, OFF and ACC positions. If PID values agree with ignition switch positions, go to next step. If values do not agree with ignition switch positions, diagnose ignition switch and circuits. See appropriate STEERING COLUMN SWITCHES article in ACCESSORIES & EQUIPMENT.

  2. Retrieve DTCs

    Turn ignition off. Connect NGS tester. Retrieve and document continuous DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under DIAGNOSIS & TESTING. Clear continuous DTCs. Retrieve on-demand DTCs. See GEM ON-DEMAND SELF-TEST  under DIAGNOSIS & TESTING. If DTCs are retrieved, go to appropriate step(s). See DTC-TO-TEST STEP INDEX  table. If no DTCs are retrieved, go to next step.
    DTC-TO-TEST STEP INDEX

    DTC Go To Test Step
    P0500  17
    P1483  10
    P1485  10
    P1812  4
    P1815  4
    P1819  13

  3. Perform Electronic Shift Functional Test

    If electronic shift functional test was completed, go to next step. If test was not completed, see ELECTRONIC SHIFT FUNCTIONAL TEST  under DIAGNOSIS & TESTING.

  4. Check 4WD Mode Switch; Monitor GEM PID 4WD_SW

    Monitor GEM PID 4WD_SW while cycling 4WD mode switch through 2WD, 4X4 HIGH and 4X4 LOW positions. If GEM PID values agree with mode switch positions, go step  10. If GEM PID values do not agree with mode switch positions, go to next step.

  5. Check Mode Switch; All Positions

    Turn ignition off. Disconnect 4WD mode switch connector. Measure resistance between terminals No. 2 and 3 (center terminals) on mode switch connector while moving mode switch through each position. See Fig 1. See MODE SWITCH RESISTANCE SPECIFICATIONS  table. If resistance is as specified, go to next step. If resistance is not as specified, replace 4WD mode switch. Clear DTCs and retest system.
    Fig 1: Identifying Mode Switch Connector Terminals
    G00006605Courtesy of FORD MOTOR CO.
    MODE SWITCH RESISTANCE SPECIFICATIONS

    Switch Position Ohms
    2WD 3700-4100
    4X4 HIGH 1050-1150
    4X4 LOW 340-380

  6. Check Circuit 465 (White/Light Blue Wire) For Open

    Disconnect GEM connector C240C (22-pin). Measure resistance of White/Light Blue wire between terminal No. 2 on 4WD mode switch connector and terminal No. 4 on GEM connector C240C (22-pin). See Figure and Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in White/Light Blue wire. Clear DTCs and retest system.

  7. Check Circuit 780 (Dark Blue Wire) For Short To Voltage

    Turn ignition on. Measure voltage between ground and Dark Blue wire at GEM 22-pin connector terminal No. 3. See Figure. If voltage is not present, go to next step. If voltage is present, repair open in Dark Blue wire. Clear DTCs and retest system.

  8. Check Circuit 780 (Dark Blue Wire) For Open

    Measure resistance of Dark Blue wire between terminal No. 3 on GEM connector C240C (22-pin) and terminal No. 2 on mode switch connector. See Figure and Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Dark Blue wire. Clears DTC and retest system.

  9. Check Circuit 780 (Dark Blue Wire) For Short To Ground

    Measure resistance of Dark Blue wire between ground and terminal No. 3 at GEM connector C240C (22-pin). If resistance is more than 10 k/ohms, go to step  20. If resistance is 10 k/ohms or less, repair Dark Blue wire. Clear DTCs and retest system.

  10. Check Brake Pedal Position (BPP) Switch Input; Monitor GEM PID BOO_GEM

    While monitoring PID BOO_GEM, depress and release brake pedal. If GEM PID BOO_GEM indicates ON with pedal depressed, and OFF with pedal released, go to step  15. If PID does not change states, go to next step.

  11. Check Brake Lights

    Depress and hold brake pedal. Check brakelights. If brakelights illuminate, go to next step. If brakelights do not illuminate, repair brakelight circuit. Clear DTCs and retest system.

  12. Check Circuit 810 (Red/Light Green Wire) For Open

    Disconnect GEM C240C connector (22-pin). Disconnect BPP switch connector. Measure resistance of Red/Light Green wire between GEM connector terminal No. 12 and terminal No. 2 on BPP switch connector. See Fig 2. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Red/Light Green wire. Clear DTCs and retest system.
    Fig 2: Identifying Brake Pedal Position Switch Connector Terminals
    G00006606Courtesy of FORD MOTOR CO.

  13. Check Digital TR Sensor

    On A/T models, while monitoring GEM PID NTRL_SW, place shift lever in "N" position. On M/T models, while monitoring GEM PIN CLTCHSW, depress clutch pedal. On A/T models, GEM PID NTRL_SW should display NTRL. On M/T models, GEM PID CLTCSW should display ENGAGD. If PID reads as specified, go to step  17. If display does not read as specified, go to next step.

  14. Check Digital TR Sensor

    Disconnect digital transmission sensor located on transmission. Monitor GEM PID NTRL_SW. Display should indicate notNTRL. Connect jumper wire between TR sensor terminal No. 8 (Red/White wire) and ground. Display should indicate GEM PID NTRL. If displays indicates NTRL, problem is in TR sensor. Repair as necessary. If display does not indicate NTRL, go to next step.

  15. Check Circuit 463 (Red/White Wire) For Open

    Disconnect GEM C240C connector (22-pin). Measure resistance of Red/White wire between TR sensor terminal No. 8 and GEM connector terminal No. 1. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Red/White wire. Clear DTCs and retest system.

  16. Check Circuit 463 (Red/White Wire) For Short To Ground

    Measure resistance between ground and Red/White wire at terminal No. 8 on TR sensor connector. If resistance is more than 10 k/ohms, go to step  20. If resistance is 10 k/ohms or less, repair Red/White wire. Clear DTCs and retest system.

  17. Check Vehicle Speed Signal; Monitor GEM PID VSS2

    Monitor ABS PID VSS2 while driving vehicle at 0-55 MPH. If PID values match speedometer readings, perform TEST A . If PID values do not match speedometer readings, go to next step.

  18. Check Speedometer

    Monitor ABS PID VSS2 while driving vehicle at 0-55 MPH. If PID values match speedometer readings, problem is in speedometer. Repair as necessary. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. If PID values do not match speedometer readings, go to next step.

  19. Check Circuit 679 (Gray/Black Wire) For Open

    Turn ignition off. Disconnect 4-Wheel ABS control module connector and central junction box C242B connector located under left side of instrument panel. Measure resistance of Gray/Black wire between 4WABS control module connector and terminal No. 21 on central junction box connector. If resistance is less than 10 k/ohms, go to next step. If resistance 10 k/ohms or more, repair open in Gray/Black wire. Clear DTCs and retest system.

  20. Check For Correct Module Operation

    Check all connectors for corrosion, pushed out pins and proper seating. Repair as necessary. Connect any disconnected connectors. Operate vehicle and verify if problem is still present. If problem is still present, replace GEM. Clear DTCs and retest system. If problem is not present, system is operating normally. Clear DTCs and retest system.
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