Possible Sources

• Wiring, terminals or connectors
• Vacuum pump relay
• ABS module

Fig 1: Antilock Braking System (ABS) Module Connector - C135

Courtesy of FORD MOTOR COMPANY

Harness Side

1. VA1: CHECK FOR BRAKE BOOSTER VACUUM SENSOR DTCS 
   • Ignition ON, engine OFF.

     Carry out the ABS self-test.

   • Is DTC C101A:15, C101A16 or C101A29 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  VA2. If DTC C101C:14 is present, Go to  VA4. For all others, No fault found. REFER to the ABS Module DTC Chart.

2. VA2: CHECK THE BRAKE BOOSTER AND VACUUM HOSES FOR LEAKS 
   • Ignition OFF.
   • Verify all the vacuum hoses are connected to their respective ports.
   • Inspect the following items for leaks:
     • brake booster-to-vacuum pump hose
     • brake booster vacuum hose elbow seal
     • brake booster vacuum sensor seal
     • brake booster-to-master cylinder seal
     • brake booster body
   • Are any leaks found? 

   Yes	No
   REPAIR or INSTALL new components as necessary. 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.

3. VA3: ISOLATE THE VACUUM PUMP RELAY 
   • Remove the vacuum pump relay.
   • Ignition ON, engine OFF.
   • Does the vacuum pump run continuously? 

   Yes	No
   REPAIR the brake vacuum pump control circuit for a short to voltage. 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.

4. VA4: CHECK THE VACUUM PUMP RELAY CONTROL CIRCUIT FOR A SHORT TO VOLTAGE 
   • Ignition OFF.
   • ABS Module connector disconnected. (C135)
   • Remove the vacuum pump relay.
   • Ignition ON, engine OFF.
   • Measure the voltage between:

     (+) Vacuum Pump Relay 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.	Go to  VA5.

5. VA5: 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
   • 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 the Anti-Lock Brake System (ABS) and Stability Control article. 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.

   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.