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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.
      • Fig 1: Checking Circuit For Voltage
      G03883128Courtesy of FORD MOTOR CO.
    • Measure the voltage between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground.
    • Is any voltage present? 
    1. YES  : TURN the parking lamps off. Go to  C2 .
    2. NO  : TURN the parking lamps off. Go to  C4 .
  2. C2 CHECK CIRCUITS 151 (LB/BK) AND 848 (DG/OG) FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: Clockspring C2274a
    • Key in ON position.
    • Turn the parking lamps on.
      • Fig 2: Checking Circuit For Voltage
      G03883128Courtesy of FORD MOTOR CO.
    • Measure the voltage between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground.
    • Is any voltage present? 
    1. YES  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
    2. 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 C2274a
    • Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM article.
    • Connect the restraint system diagnostic tool (418-F395) to the upper clockspring air bag connector.
    • Disconnect: Upper 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.
    • Connect the battery.
    • Key in ON position.
    • Turn the parking lamps on.
      • Fig 3: Checking Circuit For Voltage
      G03883128Courtesy of FORD MOTOR CO.
    • Measure the voltage between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground.
    • Is any voltage present? 
    1. YES  : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. DISCONNECT the battery. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. CLEAR the DTCs. REPEAT the self-test.
    2. 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 article. CLEAR the DTCs. REPEAT the self-test.
  4. C4 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR A SHORT TO GROUND 
    • Key in OFF position.
      • Fig 4: Checking Circuit For Short To Ground
      G03883131Courtesy of FORD MOTOR CO.
    • Measure the resistance between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground.
    • Are the resistances greater than 10,000 ohms? 
    1. YES  : Go to  C7.
    2. 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 article.
    • Disconnect: Upper Clockspring
      • Fig 5: Checking Circuit For Short To Ground
      G03883131Courtesy of FORD MOTOR CO.
    • Measure the resistance between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground.
    • Are the resistances greater than 10,000 ohms? 
    1. YES  : INSTALL a new speed control switch. REFER to Speed Control Switch . INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. CLEAR the DTCs. REPEAT the self-test.
    2. NO  : Go to  C6.
  6. C6 CHECK CIRCUITS 151 (LB/BK) AND 848 (DG/OG) FOR A SHORT TO GROUND 
    • Disconnect: Clockspring C2274a
      • Fig 6: Checking Circuit For Short To Ground
      G03883131Courtesy of FORD MOTOR CO.
    • Measure the resistance between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground.
    • Are the resistances greater than 10,000 ohms? 
    1. YES  : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. DISCONNECT the battery. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. CLEAR the DTCs. REPEAT the self-test.
    2. NO  : REPAIR the circuit in question. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. CLEAR the DTCs. REPEAT the self-test.
  7. C7 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR AN OPEN 
    • Disconnect: Clockspring C2274a
      • Fig 7: Checking Circuit For Open
      GF0017894Courtesy of FORD MOTOR CO.
    • Measure the resistance between the PCM C175b-30, circuit 151 (LB/BK), harness side and the clockspring C2274a-5, circuit 151 (LB/BK), harness side; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and the clockspring C2274a-4, circuit 848 (DG/OG), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  C8.
    2. NO  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
  8. C8 CHECK THE CLOCKSPRING 
    • Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM article.
    • Disconnect: Upper Clockspring
      • Fig 8: Checking Clockspring
      GF0017895Courtesy of FORD MOTOR CO.
    • Measure the resistance between the upper clockspring pin 3, component side and the clockspring pin 5, component side; and between the upper clockspring pin 2, component side and the clockspring pin 4, component side.
    • Are the resistances less than 5 ohms? 
    1. YES  : Go to  C9.
    2. NO  : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. DISCONNECT the battery. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. CLEAR the DTCs. REPEAT the self-test.
  9. C9 CHECK THE SPEED CONTROL SWITCH 
      Fig 9: Checking Speed Control Switch
      GF0017896Courtesy of FORD MOTOR CO.
    • Measure the resistance between the upper clockspring pin 2, harness side and the upper clockspring pin 3, harness side.
    • Is the resistance between 3,965 and 4,655 ohms? 
    1. YES  : Go to  C10.
    2. NO  : INSTALL new speed control switch. REFER to Speed Control Switch . DISCONNECT the battery. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. CLEAR the DTCs. REPEAT the self-test.
  10. C10 CHECK FOR CORRECT PCM OPERATION 
    • Disconnect all the PCM connectors.
    • Check for:
      • corrosion
      • damaged pins
      • 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? 
    1. YES  : INSTALL a new PCM. REFER to ELECTRONIC ENGINE CONTROLS article. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. TEST the system for normal operation.
    2. 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 article. CLEAR the DTCs. REPEAT the self-test.
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