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Normal Operation and Fault Conditions

The ABS module receives brake booster vacuum information directly from the brake booster vacuum sensor. When the vacuum in the booster reaches a predetermined threshold, the ABS module grounds the vacuum pump relay. The relay stays activated and the pump continues to run until the vacuum in the brake booster reaches another predetermined level. Once this second level is reached the ABS module deactivates the relay. 

An open circuit, a short to ground or voltage in any of the circuits or an internal failure in the vacuum pump relay, vacuum pump or vacuum sensor causes the pump to never run. 

PPT UA ABS MODULE DTC FAULT TRIGGER CONDITIONS

DTC Description Fault Trigger Conditions
C101C:12 Brake Vacuum Pump: Circuit Short to Battery This DTC sets if the ABS module detects a short to voltage on the brake vacuum pump relay control circuit. After the cause of this DTC is repaired, the ignition must be cycled before this DTC can be cleared from the ABS module.
C101C:14 Brake Vacuum Pump: Circuit Short to Ground or Open This DTC sets if the ABS module detects a short to ground or an open on the brake vacuum pump relay control circuit. After the cause of this DTC is repaired, the ignition must be cycled before this DTC can be cleared from the ABS module.
C101C:67 Brake Vacuum Pump: Signal Incorrect After Event The ABS module carries out a pump operation check by first reducing the vacuum in the brake booster to -10 kPa (-3 inHg), waiting 5 seconds and then increasing the vacuum in the brake booster to -65 kPa (- 19 inHg). If the vacuum in the booster does not reach -65 kPa (-19 inHg) then the ABS module sets a DTC.

Possible Sources 

Fig 1: Antilock Braking System (ABS) Module Connector - C135
G11681759Courtesy of FORD MOTOR CO.
CONNECTOR PIN REFERENCE (HARNESS SIDE)

Circuit Pin

Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may cause damage to the connector.

  1. UA1: CHECK FOR BRAKE BOOSTER VACUUM SENSOR DTCS 
    • Ignition ON, engine OFF.
    • Carry out the ABS self-test.
    • Is DTC C101A:15, C101A:16 or C101A:29 present in the ABS module? 
      Yes No
      DIAGNOSE all vacuum sensor DTCs before diagnosing any vacuum pump DTCs.
      Go to PINPOINT TEST CA .      		 If no DTCs are present or if only DTC C101C:67 is present, Go to  UA2.
      If DTC C101C:12 is present, Go to  UA7.
      If DTC C101C:14 is present, Go to  UA8. For all others, No fault found.
      REFER to the ABS Module DTC Chart.
  2. UA2: CHECK PUMP MOTOR OPERATION 
    • Ignition OFF.
    • Remove the brake vacuum pump relay.
    • Connect a 5 amp fused jumper wire between the following:
      Point A Vacuum Pump Relay Connector, Harness Side Point B Vacuum Pump Relay Connector, Harness Side
      B+ VPRO
    • Remove the jumper wire(s).
    • Does the vacuum pump run when the jumper wire is connected? 
      Yes No
      Go to  UA7. If the fused in the jumper wire opened, Go to  UA3.
      If the fused in the jumper wire did not open, Go to  UA4.
  3. UA3: CHECK THE BRAKE VACUUM PUMP CONTROL CIRCUIT FOR A SHORT TO GROUND 
    • Vacuum Pump Motor connector disconnected.
    • Measure the resistance between:
      (+) Vacuum Pump Relay Connector, Harness Side (-)
      VPRC Ground
    • Is the resistance greater than 10, 000 ohms? 
      Yes No
      INSTALL a new Vacuum Pump Motor.
      REFER to Power Brake Actuation - Brake Booster (Except Hybrid) .
      CYCLE the ignition and CARRY OUT the ABS module self-test to clear the DTC.      		 REPAIR the circuit.
      CYCLE the ignition and CARRY OUT the ABS module self-test to clear the DTC.
  4. UA4: CHECK THE VOLTAGE INPUT TO THE VACUUM PUMP RELAY 
    • Access the ABS and monitor the VPWR_ABS (VOLT) PID.
    • Measure the voltage between:
      (+) Vacuum Pump Relay Connector, Harness Side (-)
      B+ Ground
    • Is the measured voltage within 0.2 volt of the battery voltage PID display? 
      Yes No
      Go to  UA5. VERIFY BJB fuse 5 (50A) is OK.
      If OK, REPAIR the circuit.
      If not OK, REFER to the OEM Electrical Wiring Diagram Introduction (Except Hybrid) to identify the cause of the circuit short.
      CYCLE the ignition and CARRY OUT the ABS module self-test to clear the DTC.
  5. UA5: CHECK THE BRAKE VACUUM PUMP OUTPUT CIRCUIT FOR AN OPEN 
    • Measure the resistance between:
      (+) Vacuum Pump Relay Connector, Harness Side (-) Vacuum Pump Motor Connector, Harness Side
      VPRO VPRO
    • Is the resistance less than 3 ohms? 
      Yes No
      Go to  UA6. REPAIR the circuit.
      CYCLE the ignition and CARRY OUT the ABS module self-test to clear the DTC.
  6. UA6: CHECK THE BRAKE VACUUM PUMP GROUND CIRCUIT FOR AN OPEN 
    • Measure the resistance between:
      (+) Vacuum Pump Motor Connector, Harness Side (-)
      GND Ground
    • Is the resistance less than 3 ohms? 
      Yes No
      INSTALL a new Vacuum Pump Motor.
      REFER to Power Brake Actuation - Brake Booster (Except Hybrid) .
      CYCLE the ignition and CARRY OUT the ABS module self-test to clear the DTC.      		 REPAIR the circuit.
      CYCLE the ignition and CARRY OUT the ABS module self-test to clear the DTC.
      CLEAR the DTCs. REPEAT the self-test.
  7. UA7: CHECK THE VACUUM PUMP RELAY CONTROL CIRCUIT FOR A SHORT TO VOLTAGE 
    • Ignition OFF.
    • ABS Module connector disconnected. (C135)
    • Remove the brake vacuum pump relay.
    • Ignition ON, engine OFF.
    • Measure the voltage between:
      (+) Vacuum Pump Relay Connector, Harness Side (-)
      VPRC Ground
    • Is any voltage present? 
      Yes No
      REPAIR the circuit.
      CYCLE the ignition and CARRY OUT the ABS module self-test to clear the DTC.      		 INSPECT the vacuum pump relay socket for corrosion, pushed-out terminals or bent pins. REPAIR or INSTALL new as necessary. If the relay socket is OK, INSTALL a new vacuum pump relay. CYCLE the ignition and CARRY OUT the ABS module self-test to clear the DTC. If the DTC returns, Go to  UA9.
  8. UA8: CHECK THE VACUUM PUMP RELAY CONTROL CIRCUIT FOR AN OPEN 
    • Ignition OFF.
    • ABS Module connector disconnected. (C135)
    • Remove the brake vacuum pump relay.
    • Measure the voltage between:
      (+) Vacuum Pump Relay Connector, Harness Side (-) ABS Module (C135) Connector, Harness Side
      VPRC VPRC
    • Is the resistance less than 3 ohms? 
      Yes No
      INSPECT the vacuum pump relay socket for corrosion, pushed-out terminals or bent pins. REPAIR or INSTALL new as necessary. If the relay socket is OK, INSTALL a new vacuum pump relay. CYCLE the ignition and CARRY OUT the ABS module self-test to clear the DTC. If the DTC returns, Go to  UA9. REPAIR the circuit.
      CYCLE the ignition and CARRY OUT the ABS module self-test to clear the DTC.
  9. UA9: CHECK FOR CORRECT ABS MODULE OPERATION 
    • ABS Module connector disconnected. (C135) (if not previously 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
    • Vacuum Pump Motor connector connected. Make sure the connector seats and latches correctly.
    • Install the brake vacuum pump relay. Make sure the relay is fully seated.
    • ABS Module connector connected. (C135) 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
      INSTALL a new ABS module.
      CHECK OASIS for any applicable TSBs.
      If a TSB exists for this concern, DISCONTINUE this test and FOLLOW the TSB instructions.
      If no TSBs address this concern, INSTALL a new ABS module. REFER to Anti-Lock Brake System (ABS) And Stability Control (Except Hybrid) .
      ORDER a replacement ABS module and INCLUDE the RVC on the form.
      If this is a Ford paid repair, INCLUDE the RVC on the warranty claim form.
      When complete, SELECT the "X" in the top right corner to CLOSE this procedure.      		 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.
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