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

WARNING: This page is about a different car, the 2006 Mercury Milan, 2006 Lincoln Zephyr, and 2006 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
  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 C175-56, circuit VES10 (WH), harness side and ground; and between the PCM C175b-57, circuit RES08 (GN/BN), harness side and ground.
      Fig 1: Checking Speed Control Switch Circuitry For Short To Voltage
      G04684240Courtesy 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 VES10 (WH) AND RES08 (GN/BN) FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: Clockspring C218a.
    • Key in ON position.
    • Turn the parking lamps on. Measure the voltage between the PCM C175b-56, circuit VES10 (WH), harness side and ground; and between the PCM C175b-57, circuit RES08 (GN/BN), harness side and ground.
      Fig 2: Checking Circuits VES10 (WH) And RES08 (GN/BN) For Short To Voltage
      G04684241Courtesy of FORD MOTOR CO.
    • Is any voltage present? 

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

    No  : TURN the parking lamps off. 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 .
    • Disconnect: Upper Clockspring C218b.
    • Connect the restraint system diagnostic tools (418-F395) to the upper clockspring air bag connector.
    • Connect the battery.
    • Key in ON position.
    • Turn the parking lamps on.
    • Measure the voltage between the PCM C175b-56, circuit VES10 (WH), harness side and ground; and between the PCM C175b-57, circuit RES08 (GN/BN), harness side and ground.
      Fig 3: Checking Clockspring For Short To Voltage
      G04684242Courtesy of FORD MOTOR CO.
    • Is any voltage present? 

    Yes  : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . DISCONNECT the battery. 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 . DISCONNECT the battery. 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 VES10 (WH), harness side and ground; and between the PCM C175b-57, circuit RES08 (GN/BN), harness side and ground.
      Fig 4: Checking Speed Control Switch Circuitry For Short To Ground
      G04684243Courtesy 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 
    • Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM .
    • Disconnect: Upper Clockspring C218b.
    • Measure the resistance between the PCM C175b-56, circuit VES10 (WH), harness side and ground; and between the PCM C175b-57, circuit RES08 (GN/BN), harness side and ground.
      Fig 5: Checking Clockspring For Short To Ground
      G04684244Courtesy 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 VES10 (WH) AND RES08 (GN/BN) FOR A SHORT TO GROUND 
    • Disconnect: Clockspring C218a.
    • Measure the resistance between the PCM C175b-56, circuit VES10 (WH), harness side and ground; and between the PCM C175b-57, circuit RES08 (GN/BN), harness side and ground.
      Fig 6: Checking Circuits VES10 (WH) And RES08 (GN/BN) For Short To Ground
      G04684245Courtesy 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 in question. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.

  7. C7 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR AN OPEN 
    • Measure the resistance between the PCM C175b-56, circuit VES10 (WH), harness side and the PCM C175b-57, circuit RES08 (GN/BN), harness side.
      Fig 7: Checking Speed Control Switch Circuitry For Open
      G04684246Courtesy of FORD MOTOR CO.
    • Is the resistance between 4,279 and 4,363 ohms? 

    Yes  : GO to  C10.

    No  : GO to C8.

  8. C8 CHECK CIRCUITS VES10 (GN/BK) AND RES08 (GN/BN) FOR AN OPEN 
    • Disconnect: Clockspring C218a.
    • Measure the resistance between the PCM C175b-56, circuit VES10 (WH), harness side and the clockspring C218a-15, circuit VES10 (WH), harness side; and between the PCM C175b-57, RES08 (GN/BN), harness side and the clockspring C218a-14, circuit RES08 (GN/BN), harness side.
      Fig 8: Checking Circuits VES10 (GN/BK) And RES08 (GN/BN) For Open
      G04684247Courtesy of FORD MOTOR CO.
    • Are the resistances less than 5 ohms? 

    Yes  : GO to C9.

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

  9. C9 CHECK THE CLOCKSPRING 
    • Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM .
    • Measure the resistance between the clockspring C218a pin 15, component side and the upper clockspring C218b pin 8, component side; and between the clockspring C218a pin 14, component side and the upper clockspring C218b pin 9, component side.
      Fig 9: Checking Clockspring
      G04684248Courtesy of FORD MOTOR CO.
    • Are the resistances less than 5 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  : 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.

  10. C10 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 seat 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 - 2.3L or ELECTRONIC ENGINE CONTROLS - 3.0L (4V) . INSTALL the driver air bag module. REFER to ELECTRONIC ENGINE CONTROLS - 3.0L (4V) . TEST the system for normal operation.

    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 module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.

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