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Test A: No Communication With DDM

  1. Check Fuse No. 30  - Ensure transmission is in Park. Turn ignition off. Check fuse No. 30 (7.5-amp) in instrument panel fuse block. If fuse is okay, go to next step. If fuse is not okay, go to step 5).
  2. Check Voltage To Fuse Box  - Using a voltmeter, check voltage between ground and input side (left terminal) of fuse No. 30 (7.5-amp). If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, go to step 20).
  3. Check Light Green/Purple Wire For Open  - Install fuse No. 30. Disconnect DDM 22-pin connector C520 (located in upper front corner of driver's door). Using an ohmmeter, check resistance in Light Green/Purple wire between DDM 22-pin connector C520 terminal No. 29 and output side (right terminal) of fuse No. 30 (7.5-amp). See Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Light Green/Purple wire between instrument panel fuse block and DDM. Using NGS tester, repeat DDM self-test.
  4. Check Pink/Orange Wire For Open  - Using an ohmmeter, check resistance between ground and DDM 22-pin connector C520 terminal No. 23 (Pink/Orange wire). See Fig 1 . If resistance is 5 ohms or more, repair open in Pink/Orange wire and repeat DATA LINK DIAGNOSTIC TEST using NGS tester. If resistance is less than 5 ohms, repair module communications concern. See MODULE COMMUNICATIONS NETWORK - TOWN CAR article.
  5. Check Fuse No. 30  - Replace fuse No. 30 (7.5-amp) in instrument panel fuse block. DO NOT operate any switches. If fuse opens again, go to next step. If fuse does not open again, go to step 9).
  6. Check Light Green/Purple Wire For Short To Ground  - Remove fuse No. 30 (7.5-amp) from instrument panel fuse block. Disconnect DDM 22-pin connector C520 and Driver Seat Module (DSM) 26-pin connector C313 (located under driver's seat). Using an ohmmeter, check resistance between ground and DDM 22-pin connector C520 terminal No. 29 (Light Green/Purple wire). See Fig 1 . If resistance is 10 k/ohms or less, go to next step. If resistance is more than 10 k/ohms, go to step 8).
  7. Check Switches  - Check driver door lock switch, right front passenger door lock switch and luggage compartment door release switch. See POWER DOOR LOCKS & TRUNK RELEASE article. Check outside rear view mirror control switch. See POWER MIRRORS article. Check driver seat regulator control switch. See POWER SEATS article. If all switches are okay, repair short to ground in Light Green/Purple wire and repeat DDM self-test using NGS tester. If any switch(es) are not okay, replace appropriate switch and retest system operation.
  8. Check Driver Seat Module (DSM)  - Connect DSM 26-pin connector C313. Using an ohmmeter, check resistance between ground and DDM 22-pin connector C520 terminal No. 29 (Light Green/Purple wire). If resistance is more than 10 k/ohms, replace driver door module and retest system operation. If resistance is 10 k/ohms or less, replace driver seat module and retest system operation.
  9. Activate Driver & Passenger Door Lock Switches  - Lock and unlock doors using driver and right passenger door lock switches. If fuse No. 30 (7.5-amp) opens, go to next step. If fuse No. 30 (7.5-amp) is okay, go to step 12).
  10. Check Driver & Right Front Passenger Door Lock Switches  - Check driver door lock switch and right front passenger door lock switch. See POWER DOOR LOCK & TRUNK RELEASE article. If switches are okay, go to next step. If any switch is not okay, replace appropriate switch(es) and retest system operation.
  11. Check Pink/Yellow & Pink/Light Green Wires For Short To Ground  - Disconnect DDM 22-pin connector C520 (located in upper front corner of driver's door). Disconnect driver door lock switch 7-pin connector C503. Disconnect right front passenger door lock switch 7-pin connector C603. Using an ohmmeter, check resistance between ground and driver door lock switch connector C503 terminal No. 2 (Pink/Yellow wire). Also, check resistance between ground and driver door lock switch connector C503 terminal No. 6 (Pink/Light Green wire). If either or both resistance readings are 10 k/ohms or less, repair short to ground in appropriate wire(s). If both resistance readings are more than 10 k/ohms, replace driver door module and retest system operation.
  12. Activate Outside Rear View Mirror Control Switch  - Activate outside rear view mirror control switch through all positions. If fuse No. 30 (7.5-amp) opens, go to next step. If fuse No. 30 (7.5-amp) is okay, go to step 15).
  13. Check Outside Rear View Mirror Control Switch  - Check outside rear view mirror control switch. See POWER MIRRORS article. If switch is okay, go to next step. If switch is not okay, replace switch and retest system operation.
  14. Check Circuits For Short To Ground  - Disconnect DDM 22-pin connector C520 (located in upper front corner of driver's door). Disconnect outside rear view mirror control switch 10-pin connector C550. Using an ohmmeter, check resistance between ground and appropriate terminals at outside rear view mirror control switch connector C550. See MIRROR CONTROL SWITCH TERMINAL IDENTIFICATION  table. If all resistance readings are more than 10 k/ohms, replace driver door module and retest system operation. If any resistance reading are 10 k/ohms or less, repair short to ground in appropriate wire(s) and retest system operation.
    MIRROR CONTROL SWITCH TERMINAL IDENTIFICATION

    Terminal No. Wire Color
    1 Red/Orange
    2 Dark Green/Orange
    4 Yellow/Black
    8 Purple/Orange
    9 Dark Blue/Orange
  15. Activate Memory Set/Recall Switch  - Activate memory set/recall switch through all positions. If fuse No. 30 (7.5-amp) opens, go to next step. If fuse No. 30 (7.5-amp) does not open, go to step 18).
  16. Check Memory Set/Recall Switch  - Check driver seat control switch. See POWER SEATS article. If switch is okay, go to next step. If switch is not okay, replace switch and retest system operation.
  17. Check Circuits For Short To Ground  - Disconnect DDM 22-pin connector C520 and DDM 16-pin connector C521 (located in upper front corner of driver's door). Disconnect driver seat control switch 14-pin connector C509. Using an ohmmeter, check resistance between ground and terminals No. 4, 5, 6 and 7 at driver seat control switch connector C509. See DRIVER SEAT CONTROL SWITCH TERMINAL IDENTIFICATION  table. If all resistance readings are more than 10 k/ohms, replace driver door module and retest system operation. If any resistance readings are 10 k/ohms or less, repair short to ground in appropriate wire(s) and retest system operation.
    DRIVER SEAT CONTROL SWITCH TERMINAL IDENTIFICATION

    Terminal No. Wire Color
    1 Yellow/White
    2 Red/Light Blue
    3 Yellow/Light Blue
    4 White/Orange
    5 Brown/Orange
    6 Brown/Light Green
    7 Black/Orange
    9 Red/White
    11 Yellow/Light Green
    12 Red/Light Green
    13 Gray
    14 Gray/Black
  18. Activate Driver Seat Control Switch  - Activate driver seat control switch through all positions. If fuse No. 30 (7.5-amp) opens, go to next step. If fuse No. 30 (7.5-amp) does not open, system is operating properly at this time. Retest system operation.
  19. Check Circuits For Short To Ground  - Disconnect DDM 16-pin connector C521 (located in upper front corner of driver's door). Disconnect driver seat control switch 14-pin connector C509. Using an ohmmeter, check resistance between ground and terminals No. 1, 2, 3, 9, 11, 12, 13 and 14 at driver seat control switch connector C509. See DRIVER SEAT CONTROL SWITCH TERMINAL IDENTIFICATION  table. If all resistance readings are more than 10 k/ohms, replace driver door module and retest system operation. If any resistance readings are 10 k/ohms or less, repair short to ground in appropriate wire(s) and retest system operation.
  20. Check For Voltage To Power Distribution Box Fuse No. 8  - Turn ignition off. Remove maxi-fuse No. 8 (30-amp) from engine compartment power distribution box. Using a voltmeter, check voltage between ground and maxi-fuse No. 8 (30-amp) input cavity (Black/Orange wire). If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, repair Black/Orange wire and retest system operation.
  21. Check Red Wire For Open  - Remove instrument panel fuse box fuse No. 30 (7.5-amp). Disconnect driver seat module 2-pin connector C337 (located under driver's seat). Using an ohmmeter, check resistance in Red wire between engine compartment power distribution box maxi-fuse No. 8 (30-amp) output cavity and instrument panel fuse box fuse No. 30 (7.5-amp) input cavity. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Red wire and retest system operation.
  22. Check Red Wire For Short To Ground  - Using an ohmmeter, check resistance between ground and engine compartment power distribution box maxi-fuse No. 8 (30-amp) output cavity (Red wire). If resistance is more than 10 k/ohms, replace driver door module and retest system operation. If resistance is 10 k/ohms or less, repair short to ground in Red wire and retest system operation.
Fig 1: Identifying DDM Connector C520 Terminals
G98F01568Courtesy of FORD MOTOR CO.
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