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Pinpoint Test B: DTC P1703 Or DTC P1572 - Brake On/Off Circuit Failure

WARNING: This page is about a different car, the 2005 Ford Pickup, 2005 Ford F550 Super Duty, 2005 Ford F450 Super Duty, and 2005 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
  1. B1 CHECK CIRCUIT 810 (RD/LG) FOR VOLTAGE 
    • Key in OFF position.
    • Disconnect: Powertrain Control Module (PCM) C175b.
    • Key in ON position.
    • Measure the voltage between the PCM C175b-8, circuit 810 (RD/LG), harness side and ground.
      Fig 1: Measuring Voltage Between Control Module Connector And Ground
      G03889838Courtesy of FORD MOTOR CO.
    • Is any voltage present? 
    • Yes  : GO to B2.
    • No  : GO to  B5.
  2. B2 CHECK THE STOPLAMP SWITCH 
    • Key in OFF position.
    • Disconnect: Stoplamp Switch C278.
    • Key in ON position.
    • Measure the voltage between the PCM C175b-8, circuit 810 (RD/LG), harness side and ground.
      Fig 2: Measuring Voltage Between Control Module Connector And Ground
      G03889838Courtesy of FORD MOTOR CO.
    • Is any voltage present? 
    • Yes  : If equipped with automatic transmission, GO to B3.

      If equipped with four-wheel drive (4WD) manual transmission, GO to  B4.

      If equipped with two-wheel drive (2WD) manual transmission, GO to  B5.

    • No  : INSTALL a new stoplamp switch. REFER to EXTERIOR LIGHTING . CLEAR the DTCs. REPEAT the self-test.
  3. B3 CHECK THE BRAKE SHIFT INTERLOCK ACTUATOR 
    • Key in OFF position.
    • Disconnect: Brake Shift Interlock C2008.
    • Key in ON position.
    • Measure the voltage between the PCM C175b-8, circuit 810 (RD/LG), harness side and ground.
      Fig 3: Measuring Voltage Between Control Module Connector And Ground
      G03889838Courtesy of FORD MOTOR CO.
    • Is any voltage present? 
    • Yes  : If equipped with 2WD transmission, REPAIR circuit 810 (RD/LG). CLEAR the DTCs. REPEAT the self-test.

      If equipped with 4WD transmission, GO to B4.

    • No  : INSTALL a new brake shift interlock actuator. REFER to AUTOMATIC TRANSAXLE/TRANSMISSION - TORQSHIFT . CLEAR the DTCs. REPEAT the self-test.
  4. B4 CHECK THE 4WD CONTROL MODULE 
    • Key in OFF position.
    • Disconnect: 4WD Control Module C281a.
    • Key in ON position.
    • Measure the voltage between the PCM C175b-8, circuit 810 (RD/LG), harness side and ground.
      Fig 4: Measuring Voltage Between Control Module Connector And Ground
      G03889838Courtesy of FORD MOTOR CO.
    • Is any voltage present? 
    • Yes  : REPAIR circuit 810 (RD/LG). CLEAR the DTCs. REPEAT the self-test.
    • No  : GO to  B12.
  5. B5 CHECK THE BRAKE PEDAL STOPLAMP SWITCH FOR CORRECT OPERATION 
    • While applying the brake pedal, measure the voltage between the PCM C175b-8, circuit 810 (RD/LG), harness side and ground.
      Fig 5: Measuring Voltage Between Control Module Connector And Ground
      G03889838Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : GO to  B8.
    • No  : GO to B6.
  6. B6 CHECK CIRCUIT 22 (LB/BK) FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: Stoplamp Switch C278.
    • Key in ON position.
    • Measure the voltage between the stoplamp switch C278-3, circuit 22 (LB/BK), harness side and ground.
      Fig 6: Checking Circuit 22 (LB/BK) For Open
      G03924176Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : GO to B7.
    • No  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  7. B7 CHECK CIRCUIT 810 (RD/LG) FOR AN OPEN 
    • Key in OFF position.
    • Measure the resistance between the stoplamp switch C278-4, circuit 810 (RD/LG), harness side and the PCM C175b-8, circuit 810 (RD/LG), harness side.
      Fig 7: Checking Circuit 810 (RD/LG) For An Open
      G03924177Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    • Yes  : INSTALL a new stoplamp switch. REFER to EXTERIOR LIGHTING . CLEAR the DTCs. REPEAT the self-test.
    • No  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  8. B8 CHECK THE SPEED CONTROL DEACTIVATOR SWITCH FOR CORRECT OPERATION 
    • While firmly applying and releasing the brake pedal, measure the voltage between the PCM C175a-65, circuit 307 (BK/YE), harness side and ground.
      Fig 8: Measuring Voltage Between PCM C175A-65, Circuit 307 (BK/YE) And Ground
      G03889839Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts with the brake pedal released, and 0 volts with the brake pedal firmly applied? 
    • Yes  : GO to  B13.
    • No  : GO to B9.
  9. B9 CHECK CIRCUIT 418 (DG/YE) FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: Speed Control Deactivator Switch C1025.
    • Key in ON position.
    • Measure the voltage between the speed control deactivator switch C1025-2, circuit 418 (DG/YE), harness side and ground.
      Fig 9: Checking Circuit 418 (DG/YE) For An Open
      G03889840Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : GO to B10.
    • No  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  10. B10 CHECK CIRCUIT 307 (BK/YE) FOR A SHORT TO VOLTAGE 
    • Measure the voltage between the speed control deactivator switch C1025-1, circuit 307 (BK/YE), harness side and ground.
      Fig 10: Checking Circuit 307 (BK/YE) Short To Voltage
      G03919449Courtesy of FORD MOTOR CO.
    • Is any voltage present? 
    • Yes  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
    • No  : GO to B11.
  11. B11 CHECK CIRCUIT 307 (BK/YE) FOR AN OPEN 
    • Key in OFF position.
    • Measure the resistance between the speed control deactivator switch C1025-1, circuit 307 (BK/YE), harness side and the PCM C175a-65, circuit 307 (BK/YE), harness side.
      Fig 11: Checking Circuit 307 (BK/YE) For An Open
      G03889842Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    • Yes  : INSTALL a new brake master cylinder. REFER to HYDRAULIC BRAKE ACTUATION . CLEAR the DTCs. REPEAT the self-test.
    • No  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  12. B12 CHECK FOR CORRECT 4WD CONTROL MODULE OPERATION 
    • Disconnect all the 4WD control module connectors.
    • Check for:
      • corrosion
      • pushed-out pins
    • Connect all the 4WD control module 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 4WD control module. REFER to FOUR- WHEEL DRIVE SYSTEMS .
    • 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.
  13. B13 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 - GASOLINE ENGINES .
    • 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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