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Pinpoint Test O: The Brake Warning Indicator Is Always On - Vacuum Brake Booster

  1. Refer to INSTRUMENT CLUSTER for schematic and connector information.

    Normal Operation and Fault Conditions 

    See Brake Warning. REFER to: Instrument Panel Cluster (IPC) - System Operation and Component Description .

    If the brake (red) warning indicator request, brake warning indicator request or park brake lamp request messages are missing for 5 seconds longer, the IPC defaults the brake warning indicator on.

    DTC Fault Trigger Conditions 

    DTC Description Fault Trigger Condition
    BCM B1048:01 Brake Fluid Level Switch: General Electrical Failure A continuous and on-demand DTC that sets in the BCM when the BCM detects and open on the brake fluid level switch input.
    BCM B1048:7B Brake Fluid Level Switch: Low Fluid Level A continuous and on-demand DTC that sets in the BCM when the BCM detects a low brake fluid level input from the brake fluid level switch.

    Possible Sources 

    • Wiring, terminals or connectors
    • Brake fluid level switch
    • Communication concern
    • BCM
    • GWM
    • IPC

    Visual Inspection and Pre-checks 

    • Inspect the base brake system and the parking brake system for correct operation.
    • Inspect the brake fluid level switch connection and check for signs of connector terminal damage, corrosion or pushed-out pins.
    • Inspect the brake fluid level switch wiring for signs of a cut or opened circuit.
    • Inspect the brake fluid level switch for signs of any external damage.

  2. O1 RETRIEVE THE RECORDED DIAGNOSTIC TROUBLE CODES (DTCS) FROM THE IPC (INSTRUMENT PANEL CLUSTER) SELF-TEST

    • Ignition ON.

    • Using a diagnostic scan tool, perform the IPC self-test.

    Are any Diagnostic Trouble Codes (DTCs) recorded? 

    Yes  REFER to the Diagnostic Trouble Code (DTC) Chart .
    No  GO to  O2

  3. O2 RETRIEVE THE RECORDED DIAGNOSTIC TROUBLE CODES (DTCS) FROM THE BCM (BODY CONTROL MODULE) SELF-TEST

    • Using a diagnostic scan tool, perform the BCM self-test.

    Are any Diagnostic Trouble Codes (DTCs) recorded? 

    Yes  For DTC B1048:01, GO to  O5
    For DTC B1048:7B, VERIFY the brake fluid level is low. If the brake fluid level is low, CORRECT the low brake fluid condition. If the brake fluid level is not low, INSTALL a new brake fluid level switch.. For all other Diagnostic Trouble Codes (DTCs), REFER to the Diagnostic Trouble Code (DTC) Chart .
    No  GO to  O3

  4. O3 CHECK THE GWM (GATEWAY MODULE A) DIAGNOSTIC TROUBLE CODES (DTCS)

    • Using a diagnostic scan tool, check the GWM Continuous Memory Diagnostic Trouble Codes (DTCs).

    Are any Diagnostic Trouble Codes (DTCs) recorded? 

    Yes  REFER to: Controller Area Network (CAN) Module Communications Network .
    No  GO to  O4

  5. O4 CHECK THE PARKING BRAKE OPERATION

    • Check the parking brake operation while applying and releasing the parking brakes using the switch.

    Do the parking brakes apply when switched on and release when switched off? 

    Yes  GO to  O11
    No  REFER to: Parking Brake .

  6. O5 CHECK THE BRAKE FLUID LEVEL SWITCH INPUT CIRCUIT FOR A SHORT TO VOLTAGE

    • Ignition OFF.

    • Disconnect BCM C2280F.

    • Ignition ON.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C2280F-28
      GFD623860Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is any voltage present? 

    Yes  REPAIR the circuit.
    No  GO to  O6

  7. O6 CHECK THE BRAKE FLUID LEVEL SWITCH INPUT CIRCUIT FOR AN OPEN

    • Ignition OFF.

    • Disconnect Brake Fluid Level Switch C124.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C2280F-28
      GFD623861Courtesy of FORD MOTOR COMPANY
      		 C124-1

    Is the resistance less than 3 ohms? 

    Yes  GO to  O7
    No  REPAIR the circuit.

  8. O7 CHECK THE LOW BRAKE FLUID LEVEL SWITCH GROUND CIRCUIT FOR AN OPEN

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C124-2
      GFD623860Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the resistance less than 3 ohms? 

    Yes  GO to  O8
    No  REPAIR the circuit.

  9. O8 CHECK THE BRAKE FLUID LEVEL SWITCH INPUT CIRCUIT FOR A SHORT TO GROUND

    • Ignition OFF.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C2280F-28
      GFD623861Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the resistance less than 3 ohms? 

    Yes  GO to  O9
    No  GO to  O10

  10. O9 CHECK THE BRAKE FLUID LEVEL SWITCH INPUT CIRCUIT FOR A SHORT TO GROUND WITH THE BRAKE FLUID LEVEL SWITCH DISCONNECTED

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C2280F-28
      GFD623861Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the resistance greater than 10, 000 ohms? 

    Yes  INSTALL a new brake fluid level switch. REFER to: Brake Fluid Reservoir - Vehicles With: Vacuum Brake Booster .
    No  REPAIR the circuit.

  11. O10 CHECK FOR CORRECT BCM (BODY CONTROL MODULE) OPERATION

    • Ignition OFF.

    • Disconnect and inspect the BCM connectors.

    • Repair:

      • corrosion (install new connector or terminals - clean module pins)
      • damaged or bent pins - install new terminals/pins
      • pushed-out pins - install new pins as necessary

    • Reconnect the BCM connectors. Make sure they seat and latch correctly.

    • Operate the system and determine if the concern is still present.

    Is the concern still present? 

    Yes  CHECK OASIS for any applicable service articles: TSB, GSB, SSM, or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new BCM. REFER to: Body Control Module (BCM) .
    No  The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.

  12. O11 CHECK FOR CORRECT IPC (INSTRUMENT PANEL CLUSTER) OPERATION

    • Ignition OFF.

    • Disconnect and inspect the IPC connector.

    • Repair:

      • corrosion (install new connector or terminals - clean module pins)
      • damaged or bent pins - install new terminals/pins
      • pushed-out pins - install new pins as necessary

    • Reconnect the IPC connector. Make sure it seats and latches correctly.

    • Operate the system and determine if the concern is still present.

    Is the concern still present? 

    Yes  CHECK OASIS for any applicable service articles: TSB, GSB, SSM or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new IPC. REFER to: Instrument Panel Cluster (IPC) .
    No  The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.
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