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Speed Control Inoperative

WARNING: Disable air bag system before working around steering column or removing any air bag system component. See AIR BAG RESTRAINT SYSTEM article.
  1. Check Fuses  - Turn ignition off. Check instrument panel fuse block 10-amp RELAYS fuse and 10-amp ELECTRON (IGN) fuse. 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. Check For Short To Ground  - Turn ignition off. Remove instrument panel fuse block 10-amp RELAYS fuse and 10-amp ELECTRON (IGN) fuse. Disconnect Transmission Range (TR) switch connector and speed control (ON/OFF) switch connector C262. Remove speed control (ASCD HOLD) relay from relay panel located in left side of engine compartment. Using an ohmmeter, check resistance between right side terminal (Light Green wire) of 10-amp ELECTRON (IGN) fuse holder and ground. Check resistance between right side terminal (Blue wire) of 10-amp RELAYS fuse holder and ground. If resistances are more than 10 k/ohms, replace fuse(s) and go to next step. If resistances are 10 k/ohms or less, repair short to ground Light Green and/or Blue wire(s). Retest system operation.
  3. Check Blue Wire For Voltage  - Turn ignition off. Remove ASCD HOLD relay from relay panel located in left side of engine compartment. Disconnect speed control (ON/OFF) switch connector. Turn ignition on. Using a voltmeter, check voltage between ground and Blue wire terminal of ASCD HOLD relay socket. Check voltage between ground and speed control (ON/OFF) switch connector C262 terminal No. 2 (Blue wire). If voltages are more than 10 volts, reconnect connectors and go to next step. If voltages are 10 volts or less, repair Blue wire(s). Retest system operation.
  4. Check For Voltage To Speed Control Amplifier  - Turn ignition off. Disconnect speed control amplifier connector C247 located under center of dash. Turn ignition on. Using a voltmeter, check voltage between ground and speed control amplifier connector C247 terminal No. 15 (Green/White wire) while pressing buttons of speed control (ON/OFF) switch. Press ON switch. Voltage should be more than 10 volts. Press OFF switch. 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. Check Speed Control ON/OFF Switch  - Turn ignition off. Disconnect speed control ON/OFF switch connector C262. Using an ohmmeter, check resistance between specified terminals of speed control ON/OFF switch while operating 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 ON/OFF switch.
    SPEED CONTROL ACTUATOR SWITCH RESISTANCE SPECIFICATIONS

    Switch Position Check At Wire Terminals No. Standard Ohms
    ON 5-7 Less Than 5
    ON 4-5 Less Than 5
    ON 4-7 Less Than 5
    Neutral 4-5 Less Than 5
    OFF 5-7 More Than 10,000
    OFF 4-5 More Than 10,000
    OFF 4-7 More Than 10,000
    Fig 1: Identifying Speed Control ON/OFF Switch Terminals
    G94F65024Courtesy of FORD MOTOR CO.
  6. Check Circuits  - Turn ignition off. Disconnect connectors from the following: speed control ON/OFF switch, speed control amplifier and INHIBIT relay. Remove speed control (ASCD HOLD) relay. Using an ohmmeter, check resistance in Orange/Black wire between ASCD HOLD relay socket and speed control ON/OFF switch connector C262. Check resistance in Green/White wire between ASCD HOLD relay socket and speed control ON/OFF switch connector C262. Check Orange/Black and Green/White wires for short to ground. If Orange/Black wire or Green/White wire is open or shorted to ground, repair as necessary and retest system operation. If Orange/Black and Green/White wires are okay, go to next step.
  7. Check ASCD HOLD Relay Ground Circuit  - Turn ignition off. Reconnect speed control ON/OFF switch connector, speed control amplifier connector and INHIBIT relay. Remove ASCD HOLD relay. Using an ohmmeter, check resistance between ground and ASCD HOLD relay socket Black wire terminal. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Black wire. Retest system operation.
  8. Check ASCD HOLD Relay  - Turn ignition off. Remove ASCD HOLD relay. Using a jumper wire, connect terminals No. 2 and 5 of ASCD HOLD relay to positive battery terminal. See Fig 2 . Using a voltmeter, check for voltage at terminal No. 3 of ASCD HOLD relay with terminal No. 1 of relay connected to negative battery terminal. Voltage should be more 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 positive battery terminal. See Fig 2 . Check for voltage at terminal No. 6 of ASCD HOLD relay with terminal No. 1 of relay connected to negative battery terminal. Voltage should be more 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. Retest system operation.
    Fig 2: Identifying ASCD HOLD Relay Terminals
    G95B35163Courtesy of FORD MOTOR CO.
  9. Check Green/White Wire  - Turn ignition off. Disconnect ASCD HOLD relay and speed control amplifier connector C247. Using an ohmmeter, check resistance in Green/White wire between ASCD HOLD relay socket and speed control amplifier connector C247. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair Green/White wire. Retest system operation.
  10. Check Speed Control Amplifier Ground Circuit  - Turn ignition off. Disconnect speed control amplifier connector C247. Using an ohmmeter, check resistance between ground and speed control amplifier connector C247 Black wire terminal. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Black wire. Retest system operation.
  11. Check Speed Control Disengage Switch Circuit  - Turn ignition off. Remove ASCD HOLD relay. Turn ignition on. Using a voltmeter, check for voltage at White wire terminal of ASCD HOLD relay socket with brake pedal depressed. Check for voltage at White wire terminal of ASCD HOLD relay socket with brake pedal released. Voltage should be less than one volt with brake pedal depressed and more 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. Check Speed Control Disengage Switch  - Turn ignition on. Using a voltmeter, check voltage between ground and White wire terminal at harness side of speed control disengage switch connector C278 with brake pedal depressed, then released. If voltage is more than 10 volts with brake pedal released and less than one volt with brake pedal depressed, repair White wire. Retest system operation. If voltage is 10 volts or less with brake pedal released and less than one volt with brake pedal depressed, go to next step.
  13. Check For Voltage To Speed Control Disengage Switch  - Turn ignition off. Disconnect speed control disengage switch connector C278. Turn ignition on. Using a voltmeter, check for voltage between ground and speed control disengage switch connector C278 Blue wire terminal. If voltage is more than 10 volts, replace speed control disengage switch. Retest system operation. If voltage is 10 volts or less, repair Blue wire. Retest system operation.
  14. Check Brake ON/OFF Switch  - Depress and release brake pedal several times, and check stoplight operation. If stoplights are okay, go to next step. If stoplights are not okay, see appropriate EXTERIOR LIGHTS wiring diagram in SYSTEM WIRING DIAGRAMS article in the WIRING DIAGRAMS section to continue diagnosis.
  15. Check Brake ON/OFF Switch Signal  - Turn ignition off. Disconnect speed control amplifier connector C247. Depress brake pedal. Using a voltmeter, check for voltage between ground and speed control amplifier connector C247 Yellow wire terminal. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, repair Yellow wire. Retest system operation.
  16. Check Blue/White Wire  - Turn ignition off. Remove INHIBIT relay. Disconnect speed control amplifier connector C247. Using an ohmmeter, check resistance in Blue/White wire between INHIBIT relay socket and speed control amplifier connector C247. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair Blue/White wire. Retest system operation.
  17. Check INHIBIT Relay Ground Circuit  - Using an ohmmeter, check resistance between ground and INHIBIT relay socket Black wire terminal. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Black wire. Retest system operation.
  18. Check Input To INHIBIT Relay  - Turn ignition on. Using a voltmeter, check voltage between ground and INHIBIT relay socket Light Green/Black wire terminal with gear selector in Park and Neutral. Check voltage between ground and INHIBIT relay socket Light Green/Black wire terminal with gear selector in all other positions. If voltage is more than 10 volts with gear selector in Park and Neutral, and less than one volt with gear selector in all other positions, replace INHIBIT relay. If voltage is not more than 10 volts with gear selector in Park and Neutral, and less than one volt with gear selector in all other positions, go to next step.
  19. Check Light Green/Black Wire  - Turn ignition off. Disconnect Transmission Range (TR) switch connector. Remove INHIBIT relay. Using a ohmmeter, check resistance in Light Green/Black wire between TR switch connector and INHIBIT relay socket. Check resistance between ground and TR switch connector Light Green/Black wire terminal. 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 open or shorted Light Green/Black wire. Retest system operation.
  20. Check For Voltage To Transmission Range (TR) Switch  - Turn ignition off. Disconnect TR switch connector. Turn ignition on. Using a voltmeter, check voltage between ground and TR switch connector Light Green wire terminal. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, repair Light Green wire. Retest system operation.
  21. Check Transmission Range (TR) Switch  - Using an ohmmeter, check resistance between TR switch Light Green wire terminal and Light Green/Black wire terminal. Check resistance with gear selector in Park and Neutral. If resistance is less than 5 ohms with gear selector in Park and Neutral, go to next step. If resistance is 5 ohms or more with gear selector in Park and Neutral, replace TR switch. Retest system operation.
  22. Check Speed Control Switch Assembly Circuits  - 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 C247. Using a voltmeter, check voltage between ground and specified wire terminals of speed control amplifier while pressing speed control switch buttons as specified. See the SPEED CONTROL AMPLIFIER VOLTAGE SPECIFICATIONS table below. 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 Color Volts
    CANCEL
    Depressed Blue/Red More Than 10
    Depressed White/Blue More 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 More Than 10
    Released Blue/Red Less Than One
    Released White/Blue Less Than One
    RES/ACCEL
    Depressed Blue/Red More Than 10
    Depressed White/Blue Less Than One
    Released Blue/Red Less Than One
    Released White/Blue Less Than One
  23. Check Blue/Red & White/Blue Wires  - Turn ignition off. Disconnect speed control amplifier connector C247 and air bag sliding contact connector C214. Using an ohmmeter, check resistance in Blue/Red wire between speed control amplifier connector C247 and air bag sliding contact connector C214. Check resistance in White/Blue wire between speed control amplifier connector C247 and air bag sliding contact connector C214. Check resistance between ground and speed control amplifier connector C247 Blue/Red wire terminal. Check resistance between ground and speed control amplifier connector C247 White/Blue wire terminal. Resistances should be less than 5 ohms between amplifier and sliding contact, and more 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). Retest system operation.
  24. Check Speed Control Switch Assembly  - Test speed control switch. See SPEED CONTROL SWITCH ASSEMBLY under COMPONENT TESTS. If speed control switch is okay, replace air bag sliding contact and retest system operation. If speed control switch is not okay, replace speed control switch and retest system operation.
  25. Check Circuits  - Turn ignition off. Disconnect speed control amplifier connector C247 and speed control actuator connector C127. Check resistance of Brown, Light Blue, Brown/Yellow and Orange wires between speed control amplifier connector C247 and speed control actuator connector C127. Check resistance of Brown, Light Blue, Brown/Yellow and Orange wires between speed control amplifier connector C247 and ground. Resistances should be less than 5 ohms between amplifier and servo, and more 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). Retest system operation.
  26. Check Speed Control Actuator  - Test speed control actuator. See SPEED CONTROL ACTUATOR under COMPONENT TESTS. If speed control actuator is okay, replace speed control amplifier and retest system operation. If speed control actuator is not okay, replace speed control actuator and retest system operation.
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