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

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
  1. C1 CHECK THE SPEED CONTROL SWITCH CIRCUITS FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: PCM C175b
    • Key in ON position.
    • Turn the parking lamps on.
      • Fig 1: Measuring Voltage Between PCM Connector And Ground
      G03883128Courtesy of FORD MOTOR CO.
    • Measure the voltage between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, 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  C5 .
  2. C2 CHECK CIRCUITS 151 (LB/BK) AND 848 (DG/OG) FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: Clockspring C218a
    • Key in ON position.
    • Turn the parking lamps on.
      • Fig 2: Measuring Voltage Between PCM Connector And Ground
      G03883128Courtesy of FORD MOTOR CO.
    • Measure the voltage between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, circuit 848 (DG/OG), harness side and ground.
    • Is any voltage present? 
    1. YES  : REPAIR the circuit(s) in question. CLEAR the DTCs. REPEAT the self-test.
    2. NO  : Go to  C3.
  3. C3 CHECK THE CLOCKSPRING FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Connect: Clockspring C218a
    • Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM article.
    • Connect the restraint system diagnostic tool (418-F395) to the upper clockspring.
    • Disconnect: Clockspring C218b
      • WARNING: Make sure no one is in the vehicle and there is nothing blocking or placed in front of any air bag module when the battery is connected. Failure to follow these instructions may result in serious personal injury in the event of an accidental deployment.
    • Connect the battery.
    • Key in ON position.
    • Turn the parking lamps on.
      • Fig 3: Measuring Voltage Between PCM Connector And Ground
      G03883128Courtesy of FORD MOTOR CO.
    • Measure the voltage between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, 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  : Go to  C4.
  4. C4 CHECK THE STEERING WHEEL HARNESS FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Connect: Clockspring C218b
    • Disconnect: Speed Control Switch(es)
    • Key in ON position.
    • Turn the parking lamps on.
    • If equipped with remote audio/climate control switches, measure the voltage between the speed control switch C203, harness side and ground as follows:
      Speed Control Switch Circuit
      Pin 1 151 (LB/BK)
      Pin 2 848 (DG/OG)
    • If not equipped with remote audio/climate control switches, measure the voltage between the speed control switch C2330a, harness side and ground as follows:
      Speed Control Switch Circuit
      Pin 1 151 (LB/BK)
      Pin 2 133 (BK)
      Pin 3 848 (DG/OG)
    • Is any voltage present? 
    1. YES  : REPAIR the circuit in question. 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(es). 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.
  5. C5 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR A SHORT TO GROUND 
    • Key in OFF position.
      • Fig 4: Measuring Resistance Between PCM Connector And Ground
      G03883131Courtesy of FORD MOTOR CO.
    • Measure the resistance between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, circuit 848 (DG/OG), harness side and ground.
    • Are the resistances greater than 10,000 ohms? 
    1. YES  : Go to  C9.
    2. NO  : Go to  C6.
  6. C6 CHECK THE CLOCKSPRING FOR A SHORT TO GROUND 
    • Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM article.
    • Disconnect: Clockspring C218b
      • Fig 5: Measuring Resistance Between PCM Connector And Ground
      G03883131Courtesy of FORD MOTOR CO.
    • Measure the resistance between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, circuit 848 (DG/OG), harness side and ground.
    • Are the resistances greater than 10,000 ohms? 
    1. YES  : Go to  C8.
    2. NO  : Go to  C7.
  7. C7 CHECK CIRCUITS 151 (LB/BK) AND 848 (DG/OG) FOR A SHORT TO GROUND 
    • Disconnect: Clockspring C218a
      • Fig 6: Measuring Resistance Between PCM Connector And Ground
      G03883131Courtesy of FORD MOTOR CO.
    • Measure the resistance between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, 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. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. CLEAR the DTCs. REPEAT the self-test.
    2. NO  : REPAIR the circuit(s) in question. CLEAR the DTCs. REPEAT the self-test.
  8. C8 CHECK THE SPEED CONTROL SWITCH FOR A SHORT TO GROUND 
    • Disconnect: Speed Control Switch(es)
    • If equipped with remote audio/climate control switches, measure the resistance between the speed control switch C203, harness side and ground as follows:
      Speed Control Switch Circuit
      Pin 1 151 (LB/BK)
      Pin 2 848 (DG/OG)
    • If not equipped with remote audio/climate control switches, measure the resistance between the speed control switch C2330a, harness side and ground as follows:
      Speed Control Switch Circuit
      Pin 1 151 (LB/BK)
      Pin 2 133 (BK)
      Pin 3 848 (DG/OG)
    • Are the resistances greater than 10,000 ohms? 
    1. YES  : INSTALL a new speed control switch(es). 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  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
  9. C9 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR AN OPEN 
    • Measure the resistance between the PCM C175b-19, circuit 151 (LB/BK), harness side and the PCM C175b-30, circuit 848 (DG/OG), harness side.
    • Is the resistance between 3,965 and 4,655 ohms? 
    1. YES  : Go to  C13.
    2. NO  : Go to  C10.
  10. C10 CHECK CIRCUITS 151 (LB/BK) AND 848 (DG/OG) FOR AN OPEN 
    • Disconnect: Clockspring C218a
      • Fig 7: Checking Circuits For Open
      GF0014222Courtesy of FORD MOTOR CO.
    • Measure the resistance between the PCM C175b-19, circuit 151 (LB/BK), harness side and the clockspring C218a-13, circuit 151 (LB/BK), harness side; and between the PCM C175b-30, circuit 848 (DG/OG), harness side and the clockspring C218a-3, circuit 848 (DG/OG), harness side.
    • Are the resistances less than 5 ohms? 
    1. YES  : Go to  C11.
    2. NO  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
  11. C11 CHECK THE CLOCKSPRING 
    • Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM article.
    • Disconnect: Clockspring C218b
      • Fig 8: Checking Clockspring
      GF0014223Courtesy of FORD MOTOR CO.
    • Measure the resistance between the clockspring C218b pin 11, component side and the clockspring C218a pin 3, component side; and between the clockspring C218b pin 3, component side and the clockspring C218a pin 13, component side.
    • Are the resistances less than 5 ohms? 
    1. YES  : Go to  C12.
    2. NO  : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM article. CLEAR the DTCs. REPEAT the self-test.
  12. C12 CHECK THE STEERING WHEEL HARNESS 
    • Disconnect: Speed Control Switch(es)
    • If equipped with remote audio/climate control switches, measure the resistance between the clockspring C218b, harness side and the speed control switch C203, harness side as follows:
      Clockspring Connector-Pin Speed Control Switch Connector-Pin Circuit
      C218b-3 C203-1 151 (LB/BK)
      C218b-11 C203-2 848 (DG/OG)
    • If not equipped with remote audio/climate control switches, measure the resistance between the clockspring C218b, harness side and the speed control switch; and between the speed control switch C2330a, harness side and the speed control switch C2330b, harness side as follows:
      Clockspring Connector-Pin Speed Control Switch Connector-Pin Speed Control Switch Connector-Pin Circuit
      C218b-3 C2330a-1 - 151 (LB/BK)
      C218b-3 - C2330b-6 151 (LB/BK)
      C218b-11 C2330a-3 - 848 (DG/OG)
      C218b-11 - C2330b-4 848 (DG/OG)
      - C2330a-2 C2330b-5 133 (BK)
    • Are the resistances less than 5 ohms? 
    1. YES  : INSTALL new speed control switch(es). REFER to Speed Control Switch . CLEAR the DTCs. REPEAT the self-test.
    2. NO  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
  13. C13 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 seat 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. 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. CLEAR the DTCs. REPEAT the self-test.
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