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Pinpoint Test A - Speed Control Inoperative

WARNING: This page is about a different car, the 1996 Mercury Villager. However, it is still accessible from the selected car via links, so may be relevant.
WARNING: Disable air bag system before working around steering column or removing any air bag system component. See appropriate AIR BAG RESTRAINT SYSTEM article.
  1. Turn ignition off. Check 10-amp RELAYS fuse and 10-amp ELECTRON fuse located in interior fuse junction panel. If fuses are okay, go to step 3). If either fuse is blown, turn ignition off and replace blown fuse. Turn ignition on and recheck fuses. If any fuse blows again, go to next step. If fuses are okay, go to step 3).
  2. Turn ignition off. Remove 10-amp RELAYS fuse and/or 10-amp ELECTRON fuse. Disconnect Transmission Range (TR) switch connectors and speed control actuator switch connector. Remove speed control (ASCD HOLD) relay from relay panel located in left side of engine compartment. Measure resistance of Light Green wire between right side terminal of ELECTRON fuse holder and ground. Measure resistance of Blue wire between right side terminal of RELAYS fuse holder and ground. If resistances are greater than 10 k/ohms, replace fuse(s) and go to next step. If resistances are less than 10 k/ohms, repair Light Green and/or Blue wire(s).
  3. Turn ignition off. Remove ASCD HOLD relay from relay panel located in left side of engine compartment. Disconnect speed control actuator switch connector. Turn ignition on. Measure voltage at Blue wire terminal of ASCD HOLD relay connector. Measure voltage at Blue wire terminal of speed control actuator switch connector. If voltages are greater than 10 volts, reconnect all connectors and go to next step. If voltages are less than 10 volts, repair Blue wire(s).
  4. Turn ignition off. Disconnect speed control amplifier connector located under center of dash. Turn ignition on. Measure voltage at Green/White wire terminal of speed control amplifier connector while pressing buttons of speed control actuator switch. With actuator ON switch depressed and held in ON position, and released after being held on, voltage should be greater than 10 volts. With actuator OFF switch depressed and held in OFF position, and released after being held off, voltage should be less than one volt. If voltages are as specified, go to step 10). If voltages are not as specified, go to next step.
  5. Turn ignition off. Disconnect speed control actuator switch connector. Measure resistance between specified wire terminals of speed control actuator switch connector while pressing switch as specified. See Fig 1 . See SPEED CONTROL ACTUATOR SWITCH RESISTANCE SPECIFICATIONS  table. If resistances are as specified, go to next step. If resistances are not as specified, replace speed control actuator switch.
    SPEED CONTROL ACTUATOR SWITCH RESISTANCE SPECIFICATIONS

    Switch Position Wire Terminal No. Ohms
    ON 5-7 Less Than 5
    ON 5-4 Less Than 5
    ON 7-4 Less Than 5
    Neutral 5-4 Less Than 5
    OFF 5-7 Greater Than 10,000
    OFF 5-4 Greater Than 10,000
    OFF 7-4 Greater Than 10,000
    Fig 1: Identifying Speed Control Actuator Switch Connector Terminals
    G94F65024Courtesy of FORD MOTOR CO.
  6. Turn ignition off. Disconnect connectors from the following: speed control actuator switch, speed control amplifier and INHIBIT relay. Remove ASCD HOLD relay. Measure resistance of Orange/Black wire between terminal No. 2 of ASCD HOLD relay connector and speed control actuator switch connector. Measure resistance of Green/White wire between terminal No. 3 of ASCD HOLD relay connector and speed control actuator switch connector. Measure resistance of Orange/Black wire between speed control actuator switch connector and ground. Measure resistance of Green/White wire between speed control actuator switch connector and ground. Resistances should be less than 5 ohms between relay and switch, and greater than 10 k/ohms between switch and ground. If resistances are as specified, go to next step. If resistances are not as specified, repair Orange/Black and/or Green/White wire(s).
  7. Turn ignition off. Reconnect speed control actuator switch connector, speed control amplifier connector and INHIBIT relay connector. Remove ASCD HOLD relay. Measure resistance of Black wire between terminal No. 1 of ASCD HOLD relay connector and ground. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair Black wire.
  8. Turn ignition off. Remove ASCD HOLD relay. Using a jumper wire, connect terminals No. 2 and 5 of ASCD HOLD relay to battery positive terminal. See Fig 2 . Measure voltage at terminal No. 3 of ASCD HOLD relay with terminal No. 1 of relay connected to negative battery terminal. Voltage should be greater than 10 volts. Disconnect terminal No. 1 from negative battery terminal. Voltage should be less than one volt. Using a jumper wire, connect terminals No. 2 and 7 of ASCD HOLD relay to battery positive terminal. See Fig 2 . Measure voltage at terminal No. 6 of ASCD HOLD relay with terminal No. 1 of relay connected to negative battery terminal. Voltage should be greater than 10 volts. Disconnect terminal No. 1 from negative battery terminal. Voltage should be less than one volt. If voltages are as specified, go to next step. If voltages are not as specified, replace ASCD HOLD relay.
    Fig 2: Identifying ASCD HOLD Relay Terminals
    G95B35163Courtesy of FORD MOTOR CO.
  9. Turn ignition off. Disconnect ASCD HOLD relay and speed control amplifier connectors. Measure resistance of Green/White wire between ASCD HOLD relay connector and speed control amplifier connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair Green/White wire.
  10. Turn ignition off. Install ASCD HOLD relay. Disconnect speed control amplifier connector. Measure resistance of Black wire between speed control amplifier connector and ground. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair Black wire.
  11. Turn ignition off. Disconnect ASCD HOLD relay connector. Turn ignition on. Measure voltage at White wire terminal of ASCD HOLD relay connector with brake pedal depressed. Measure voltage at White wire terminal of ASCD HOLD relay connector with brake pedal released. Voltage should be less than one volt with brake pedal depressed and greater than 10 volts with brake pedal released. If voltage is as specified, go to step 14). If voltage is not as specified, go to next step.
  12. Turn ignition on. Measure voltage between White wire terminal at harness side of speed control disengage switch connector and ground with brake pedal depressed, then released. If voltage is greater than 10 volts with brake pedal released and less than one volt with brake pedal depressed, repair White wire. If voltage is not greater than 10 volts with brake pedal released and less than one volt with brake pedal depressed, go to next step.
  13. Turn ignition off. Disconnect speed control disengage switch connector. Turn ignition on. Measure voltage between Black wire terminal of speed control disengage switch connector and ground. If voltage is greater than 10 volts, replace speed control disengage switch. If voltage is less than 10 volts, repair Black wire.
  14. Depress and release brake pedal several times, and check stoplight operation. If stoplights are okay, go to next step. If stoplight are not okay, diagnose and repair as necessary.
  15. Turn ignition off. Disconnect speed control amplifier connector. Depress brake pedal. Measure voltage at Yellow wire terminal of speed control amplifier connector. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair Yellow wire.
  16. Turn ignition off. Remove INHIBIT relay. Disconnect speed control amplifier connector. Measure resistance of Blue/White wire between INHIBIT relay connector and speed control amplifier connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair Blue/White wire.
  17. Turn ignition off. Disconnect INHIBIT relay connector. Measure resistance of Black wire between INHIBIT relay connector and ground. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair Black wire.
  18. Turn ignition off. Disconnect INHIBIT relay connector. Turn ignition on. Measure voltage at Light Green/Black wire terminal of INHIBIT relay connector with gear selector in Park and Neutral positions. Measure voltage at Light Green/Black wire terminal of INHIBIT relay connector with gear selector in all other positions. If voltage is greater than 10 volts with gear selector in Park and Neutral positions, and less than one volt with gear selector in all other positions, replace INHIBIT relay. If voltage is not greater than 10 volts with gear selector in Park and Neutral positions, and less than one volt with gear selector in all other positions, go to next step.
  19. Turn ignition off. Disconnect Transmission Range (TR) switch connector and INHIBIT relay connector. Measure resistance of Light Green/Black wire between TR switch connector and INHIBIT relay connector. Measure resistance of Light Green/Black wire between TR switch connector and ground. Resistances should be less than 5 ohms between switch and relay, and greater than 10 k/ohms between switch and ground. If resistances are as specified, go to next step. If resistances are not as specified, repair Light Green/Black wire(s).
  20. Turn ignition off. Disconnect TR switch connector. Turn ignition on. Measure voltage at Light Green wire terminal of TR switch connector. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair Light Green wire.
  21. Measure resistance between Light Green wire terminal and Light Green/Black wire terminal of TR switch. Measure resistance with gear selector in Park and Neutral positions. If resistance is less than 5 ohms with gear selector in Park and Neutral positions, go to next step. If resistance is greater than 5 ohms with gear selector in Park and Neutral positions, replace TR switch.
  22. Turn ignition off. Install INHIBIT relay. Check operation of horn. If horn does not operate, diagnose and repair as necessary. Disconnect speed control amplifier connector. Measure voltage at specified wire terminals of speed control amplifier while pressing speed control switch buttons as specified. See SPEED CONTROL AMPLIFIER VOLTAGE SPECIFICATIONS table. Press only one button at a time. If voltages are as specified, go to step 25). If voltages are not as specified, go to next step.
    SPEED CONTROL AMPLIFIER VOLTAGE SPECIFICATIONS

    Switch Position Wire Volts
    CANCEL
    Depressed Blue/Red Greater Than 10
    Depressed White/Blue Greater Than 10
    Released Blue/Red Less Than One
    Released White/Blue Less Than One
    COAST/SET
    Depressed Blue/Red Less Than One
    Depressed White/Blue Greater Than 10
    Released Blue/Red Less Than One
    Released White/Blue Less Than One
    RES/ACCEL
    Depressed Blue/Red Greater Than 10
    Depressed White/Blue Less Than One
    Released Blue/Red Less Than One
    Released White/Blue Less Than One
  23. Turn ignition off. Disconnect speed control amplifier connector and air bag sliding contact connector. Measure resistance of Blue/Red wire between speed control amplifier connector and air bag sliding contact connector. Measure resistance of White/Blue wire between speed control amplifier connector and air bag sliding contact connector. Measure resistance of Blue/Red wire between speed control amplifier connector and ground. Measure resistance of White/Blue wire between speed control amplifier connector and ground. Resistances should be less than 5 ohms between amplifier and sliding contact, and greater than 10 k/ohms between amplifier and ground. If resistances are as specified, go to next step. If resistances are not as specified, repair Blue/Red and/or White/Blue wire(s).
  24. Test speed control switch. See the SPEED CONTROL SWITCH ASSEMBLY  under TESTING. If speed control switch is okay, replace air bag sliding contact. If speed control switch is not okay, replace speed control switch.
  25. Turn ignition off. Disconnect speed control amplifier connector and speed control servo connector. Measure resistance of Brown, Light Blue, Brown/Yellow and Orange wires between speed control amplifier connector and speed control servo connector. Measure resistance of Brown, Light Blue, Brown/Yellow and Orange wires between speed control amplifier connector and ground. Resistances should be less than 5 ohms between amplifier and servo, and greater than 10 k/ohms between amplifier and ground. If resistances are as specified, go to next step. If resistances are not as specified, repair Brown, Light Blue, Brown/Yellow and/or Orange wire(s).
  26. Test speed control servo. See SPEED CONTROL SERVO  under TESTING. If speed control servo is okay, replace speed control amplifier. If speed control servo is not okay, replace speed control servo.
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