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HOMESERVICE MANUALSFORD2021TRANSIT-150 XLT, 3.5L ENG VIN 8, AWDREPAIR AND DIAGNOSIS (SINGLE PAGE)BRAKESBRAKES CONTROL SYSTEMSABS GUIDED ROUTINE - PINPOINT TESTS C - FPINPOINT TESTS C: BRAKE BOOSTER VACUUM SENSOR FAULTSVISUAL INSPECTION AND DIAGNOSTIC PRE-CHECKS
2021 Ford Transit-150 XLT, 3.5L Eng VIN 8, AWD

Visual Inspection And Diagnostic Pre-Checks

2021 Ford Transit-150 XLT, 3.5L Eng VIN 8, AWDSECTION Visual Inspection And Diagnostic Pre-Checks
  • Inspect the brake booster for vacuum leaks.
  • Inspect the brake booster for any obvious signs of damage.
  • Inspect the brake booster vacuum sensor harness and connector of any obvious signs of damage.
  • Make sure the brake booster vacuum sensor electrical connector is free from any corrosion or other contaminants.
NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may cause damage to the connector.
  1. C1: VERIFY ALL WIRING CONNECTIONS 
    • Ignition OFF.
    • ABS Module connector disconnected.
    • Brake Booster Vacuum Sensor connector disconnected.
    • Using a good light source, inspect each connector terminal for any corrosion.
    • Inspect both connectors for any pushed-out pins. Refer to the Connector Repair Procedures wiring diagrams for schematic and connector information.
    • Are both connectors free of corrosion, pushed-out pins and deformed or enlarged contacts? 
    Yes No
    Go to  C2. REPAIR the terminals in question.
  2. C2: VERIFY THE ABS MODULE DTCS 
    • ABS Module connector connected. Make sure the connector seats and latches correctly.
    • Brake Booster Vacuum Sensor connector connected. Make sure the connector seats and latches correctly.
    • Ignition ON, engine OFF.
    • Clear the ABS DTCs.
    • Ignition OFF.
    • Ignition ON, engine OFF.

      Carry out the ABS self-test.

    • Are any DTCs from the DTC Fault Trigger Conditions Table present? 
    Yes No
    Go to  C3. Go to  C4.
  3. C3: CHECK THE BRAKE BOOSTER AND VACUUM HOSES FOR LEAKS 
    • Inspect the vacuum hoses, brake booster and brake booster seals for leaks or evidence of leaks.
    • Are the vacuum hoses, brake booster and brake booster seals free from leaks? 
    Yes No
    Go to  C4. REPAIR or INSTALL new components as necessary.
  4. C4: CHECK THE VACUUM SENSOR WIRING FOR A SHORT TO VOLTAGE 
    • Ignition OFF.
    • ABS Module connector disconnected.
    • Brake Booster Vacuum Sensor connector disconnected.
    • Ignition ON, engine OFF.
    • Measure the voltage between:
      (+) ABS Module Connector, Harness Side (-)
      VREF Ground
      SIGRTN Ground
      SRef Ground
      VAC SNS P Ground
      VAC SIG Ground
      VAC GND Ground
    • Is any voltage present? 
    Yes No
    REPAIR the circuit in question. Go to  C5.
  5. C5: CHECK THE VACUUM SENSOR WIRING FOR A SHORT TO GROUND 
    • Ignition OFF.
    • Measure the resistance between:
      (+) ABS Module Connector, Harness Side (-)
      VREF Ground
      SIGRTN Ground
      SRef Ground
      VAC SNS P Ground
      VAC SIG Ground
      VAC GND Ground
    • Are the resistances greater than 10,000 ohms? 
    Yes No
    Go to  C6. REPAIR the circuit in question.
  6. C6: CHECK THE VACUUM SENSOR WIRING FOR AN OPEN 
    • Measure the resistance between:
      (+) ABS Module Connector, Harness Side (-) Brake Booster Vacuum Sensor Connector, Harness Side
      VREF VREF
      SIGRTN SIGRTN
      SRef SRef
      VAC SNS P VAC SNS P
      VAC SIG VAC SIG
      VAC GND VAC GND
    • Are the resistances less than 3 ohms? 
    Yes No
    Go to  C7. REPAIR the circuit in question.
  7. C7: CHECK THE VACUUM SENSOR WIRING FOR A SHORT TOGETHER 
    • Measure the resistance between:
      (+) Brake Booster Vacuum Sensor Connector, Harness Side (-) Brake Booster Vacuum Sensor Connector, Harness Side
      SRef SIGRTN
      SRef VREF
      SIGRTN VREF
      VAC SNS P VAC SIG
      VAC SNS P VAC GND
      VAC SIG VAC GND
    • Are the resistances greater than 10,000 ohms? 
    Yes No
    Go to  C8. REPAIR the circuits in question.
  8. C8: CHECK THE MODULE OUTPUT 
    • ABS Module connector connected. Make sure the connector seats and latches correctly.
    • Ignition ON, engine OFF.
    • Measure the voltage between:
    (+) Brake Booster Vacuum Sensor Connector, Harness Side (-)
    VREF Ground
    VAC SNS P Ground
    Yes No
    INSTALL a new brake booster vacuum sensor. Go to  C9.
  9. C9: VERIFY ALL WIRING CONNECTIONS 
    • Ignition OFF.
    • ABS Module connector disconnected.
    • Using a good light source, inspect all disconnected electrical connectors for the following:
      • corrosion - install new connector or terminal and clean the module pins.
      • damaged or bent pins - install new terminals or pins.
      • pushed-out pins - install new pins as necessary.
      • spread terminals - install new terminals as necessary.
    • Are the connectors free of corrosion, damaged pins, bent pins, pushed-out pins and spread terminals? 
    Yes No
    Go to  C10. REPAIR the connector or terminals. Refer to the Connector Repair Procedures wiring diagrams for schematic and connector information.
  10. C10: CHECK FOR CORRECT ABS MODULE OPERATION 
    • Ignition OFF.
    • Brake Booster Vacuum Sensor connector connected. Make sure the connector seats and latches correctly.
    • ABS Module connector connected. Make sure the connector seats and latches correctly.
    • Operate the system and determine if the concern is still present.
    • Is the concern still present? 
    Yes No
    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 ABS module. REFER to the Anti-Lock Brake System (ABS) and Stability Control article.    		 The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.