1990 Ford Taurus SHOFACTORY OEM SERVICE PROCEDURE

Test C, Keypad Input

This test checks keypad, keyless entry module, Brown connector, Gray connector and related circuits.

  1. Disconnect keypad and Brown connector. Check circuit corresponding to the failing button for short to ground (100K ohms or less) between Brown module connector. See KEYPAD INPUT TEST table. If short is found, go to step 3). If no short is found, go to next step.
  2. Disconnect Brown module connector. Check for short between malfunctioning button and Gray or Brown connector on circuit No. 124 (Brown wire). If no short is found, go to step 4). If short is found, replace keypad and repeat QUICK TEST.
  3. Remove door trim panel. Disconnect keypad connector. Check circuit corresponding to malfunctioning button for resistance of less than 100K ohms between keypad connector and ground. If resistance to ground or circuit No. 124 (Brown wire) is low, replace switch. If resistance is not low, repair harness between Gray or Brown connector and keypad connector. Repeat QUICK TEST.
    KEYPAD INPUT TEST

    Key Circuit No. Pin No.
    1/2 78 3
    3/4 79 4
    5/6 121 5
    7/8 122 6
    9/0 123 7
  4. With 1/2 button depressed, verify that circuit No. 124 (Brown wire) between Gray or Brown connector and keypad connector is not shorted to ground or open. If wire is okay, go to step 5). If not, repair open or short in wire and repeat QUICK TEST.
  5. Connect module connector. Connect voltmeter between pin No. 1 of Brown or Gray connector and ground. For each button that failed to light on keypad, connect a jumper wire for 5 seconds between pin No. 12 of Gray or Brown connector and keypad pins No. 3 through 7. If readings are 5 volts or more, go to step 6). If not, replace keyless entry module and repeat QUICK TEST.
  6. Remove door trim panel. Disconnect keypad connector. Check for 10 ohms or less between pins No. 1 and 8 of keypad. If reading is 10 ohms or more, replace keypad and repeat QUICK TEST. If reading is less than 10 ohms, go to step 7). If reading is more than 10 Ohms, replace keypad and repeat QUICK TEST.
  7. Check for continuity between every pair of keypad pins until all pin pairs have been checked. If all circuits are open except those between pins No. 1 and 8, go to step 8). If a short is found, replace keypad and repeat QUICK TEST.
  8. Check wiring harness to keypad connector for opens or shorts. See WIRING DIAGRAMSΒ  . Repair as necessary.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.

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