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Pinpoint Test C: DTC P0579 Or DTC P0581 - Speed Control Switch Circuit Failure

  1. C1 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: PCM C175b.
    • Key in ON position.
    • Turn the parking lamps on.
    • Measure the voltage between the PCM C175b-56, circuit 31S-PG24 (BK/OG), harness side and ground; and between the PCM C175b-57, circuit 7-PG24 (YE/BU), harness side and ground.
      Fig 1: Checking Speed Control Switch Circuitry For Short To Voltage
      G04691910Courtesy of FORD MOTOR CO.
    • Is any voltage present? 

    Yes  : TURN the parking lamps off. GO to C2  .

    No  : TURN the parking lamps off. GO to  C4.

  2. C2 CHECK CIRCUITS 7-PG24 (YE/BU) AND 31S-PG24 (BK/OG) FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: Clockspring C218a.
    • Key in ON position.
    • Measure the voltage between the PCM C175b-56, circuit 31S-PG24 (BK/OG), harness side and ground; and between the PCM C175b-57, circuit 7-PG24 (YE/BU), harness side and ground.
      Fig 2: Checking Circuits 7-PG24 (YE/BU) And 31S-PG24 (BK/OG) For Short To Voltage
      G04691911Courtesy of FORD MOTOR CO.
    • Is any voltage present? 

    Yes  : REPAIR the circuit(s) in question. CLEAR the DTCs. REPEAT the self-test.

    No  : GO to C3  .

  3. C3 CHECK THE CLOCKSPRING FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Connect: Clockspring C218a.
      • WARNING: Make sure there is no one inside the vehicle and that there is nothing blocking or set in front of any air bag module when the battery is connected. Failure to follow these instructions may result in personal injury.
    • Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM .
    • Connect the restraint system diagnostic tool to the upper clockspring air bag connector.
    • Disconnect: Upper Clockspring.
    • Connect the battery.
    • Key in ON position.
    • Turn the parking lamps on.
    • Measure the voltage between the PCM C175b-56, circuit 31S-PG24 (BK/OG), harness side and ground; and between the PCM C175b-57, circuit 7-PG24 (YE/BU), harness side and ground.
      Fig 3: Checking Clockspring For Short To Voltage
      G04691912Courtesy of FORD MOTOR CO.
    • Is any voltage present? 

    Yes  : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.

    No  : INSTALL a new speed control switch. REFER to SPEED CONTROL SWITCH . INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.

  4. C4 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR A SHORT TO GROUND 
    • Key in OFF position.
    • Measure the resistance between the PCM C175b-56, circuit 31S-PG24 (BK/OG), harness side and ground; and between the PCM C175b-57, circuit 7-PG24 (YE/BU), harness side and ground.
      Fig 4: Checking Speed Control Switch Circuitry For Short To Ground
      G04691913Courtesy of FORD MOTOR CO.
    • Are the resistances greater than 10,000 ohms? 

    Yes  : GO to  C7.

    No  : GO to C5  .

  5. C5 CHECK THE CLOCKSPRING FOR A SHORT TO GROUND 
      WARNING: Make sure there is no one inside the vehicle and that there is nothing blocking or set in front of any air bag module when the battery is connected. Failure to follow these instructions may result in personal injury.
    • Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM .
    • Disconnect: Upper Clockspring.
    • Measure the resistance between the PCM C175b-56, circuit 31S-PG24 (BK/OG), harness side and ground; and between the PCM C175b-57, circuit 7-PG24 (YE/BU), harness side and ground.
      Fig 5: Checking Clockspring For Short To Ground
      G04691914Courtesy of FORD MOTOR CO.
    • Are the resistances greater than 10,000 ohms? 

    Yes  : INSTALL a new speed control switch. REFER to SPEED CONTROL SWITCH . INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.

    No  : GO to C6  .

  6. C6 CHECK CIRCUITS 7-PG24 (YE/BU) AND 31S-PG24 (BK/OG) FOR A SHORT TO GROUND 
    • Disconnect: Clockspring C218b.
    • Key in OFF position.
    • Measure the resistance between the PCM C175b-56, circuit 31S-PG24 (BK/OG), harness side and ground; and between the PCM C175b-57, circuit 7-PG24 (YE/BU), harness side and ground.
      Fig 6: Checking Circuits 7-PG24 (YE/BU) And 31S-PG24 (BK/OG) For Short To Ground
      G04691915Courtesy of FORD MOTOR CO.
    • Are the resistances greater than 10,000 ohms? 

    Yes  : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.

    No  : REPAIR the circuit(s) in question. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test

  7. C7 CHECK CIRCUITS 7-PG24 (YE/BU) AND 31S-PG24 (BK/OG) FOR AN OPEN 
    • Measure the resistance between the PCM C175b-56, circuit 31S-PG24 (BK/OG), harness side and the clockspring C218a-3, circuit 31S-PG24 (BK/OG), harness side; and between the PCM C175b-57, circuit 7-PG24 (YE/BU), harness side and the clockspring C218a-4, circuit 7-PG24 (YE/BU), harness side.
      Fig 7: Checking Circuits 7-PG24 (YE/BU) And 31S-PG24 (BK/OG) For Open
      G04691916Courtesy of FORD MOTOR CO.
    • Are the resistances less than 5 ohms? 

    Yes  : GO to C8  .

    No  : REPAIR the circuit(s) in question. CLEAR the DTCs. REPEAT the self-test.

  8. C8 CHECK THE CLOCKSPRING 
      WARNING: Make sure there is no one inside the vehicle and that there is nothing blocking or set in front of any air bag module when the battery is connected. Failure to follow these instructions may result in personal injury.
    • Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM .
    • Disconnect: Upper Clockspring.
    • Measure the resistance between the clockspring connector C218a pin 3, component side and the upper clockspring connector pin 3, component side; and between the clockspring C218a pin 4, component side and the upper clockspring connector pin 4, component side.
      Fig 8: Checking Clockspring
      G04691917Courtesy of FORD MOTOR CO.
    • Are the resistances less than 5 ohms? 

    Yes  : GO to C9  .

    No  : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.

  9. C9 CHECK FOR CORRECT PCM OPERATION 
    • Disconnect all the PCM connectors.
    • Check for:
      • Corrosion
      • Pushed-out pins
    • Connect all the PCM connectors and make sure they are seated correctly.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 

    Yes  : INSTALL a new PCM. REFER to ELECTRONIC ENGINE CONTROLS . INSTALL the driver air bag. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . REPEAT the self-test.

    No  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. INSTALL the driver air bag. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.

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