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.

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

Courtesy of FORD MOTOR COMPANY

CONNECTOR PIN REFERENCE (HARNESS SIDE)

Circuit	Pin
VREF (Reference Voltage) - LCA37	44 (YELLOW/ORANGE)
SIGRTN (Signal Return) - RCA37	45 (WHITE/BLUE)
SRef (Signal Reference Voltage) - VCA38	36 (BROWN/VIOLET)

Fig 2: Brake Booster Vacuum Sensor Connector - C149

Courtesy of FORD MOTOR CO.

CONNECTOR PIN REFERENCE (HARNESS SIDE)

Circuit	Pin
VREF (Reference Voltage) - LCA37	3 (YELLOW/ORANGE)
SIGRTN (Signal Return) - RCA37	2 (WHITE/BLUE)
SRef (Signal Reference Voltage) - VCA38	1 (BROWN/VIOLET)

1. C1: VERIFY ALL WIRING CONNECTIONS 
   • Ignition OFF.
   • ABS Module connector disconnected. (C135)
   • Brake Booster Vacuum Sensor connector disconnected. (C149)
   • Using a good light source, inspect each connector terminal for any corrosion.
   • Inspect both connectors for any pushed-out pins. Refer to OEM CONNECTOR REPAIR PROCEDURES (EXCEPT HYBRID) , for schematic and connector information.
   • Using a suitable mating terminal, check each female terminal for deformed or enlarged contacts by comparing the mating terminal's fit between each of the following pins:
     • C135-36
     • C135-44
     • C135-45
     • C149-1
     • C149-2
     • C149-3
   • 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: CHECK THE ABS MODULE DTCS 
   • ABS Module connector connected. (C135)
   • Brake Booster Vacuum Sensor connector connected. (C149)
   • Ignition ON, engine OFF.
   • Carry out the ABS self-test.
   • Is DTC C0021:09, C0047:26 or C0047:64 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. (C135)
   • Brake Booster Vacuum Sensor connector disconnected. (C149)
   • Ignition ON, engine OFF.
   • Measure the voltage between:

     (+) ABS Module (C135) Connector, Harness Side	(-)
     VREF - LCA37 (YELLOW/ORANGE) - Pin 44	Ground
     SIGRTN - RCA37 (WHITE/BLUE) - Pin 45	Ground
     SRef - VCA38 (BROWN/VIOLET) - Pin 36	Ground

   • Measure the voltage between:

     (+) PCM_B (C1915B) Connector, Harness Side	(-)
     VAC GND	Ground
     VAC SIG	Ground
     VAC SNS P	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 (C135) Connector, Harness Side	(-)
     VREF - LCA37 (YELLOW/ORANGE) - Pin 44	Ground
     SIGRTN - RCA37 (WHITE/BLUE) - Pin 45	Ground
     SRef - VCA38 (BROWN/VIOLET) - Pin 36	Ground

   • Measure the resistance between:

     (+) PCM B (C1915B) Connector, Harness Side	(-)
     VAC GND	Ground
     VAC SIG	Ground
     VAC SNS P	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 (C135) Connector, Harness Side	(-) Brake Booster Vacuum Sensor (C149) Connector, Harness Side
     VREF - LCA37 (YELLOW/ORANGE) - Pin 44	VREF - LCA37 - Pin 3
     SIGRTN - RCA37 (WHITE/BLUE) - Pin 45	SIGRTN - RCA37 - Pin 2
     SRef - VCA38 (BROWN/VIOLET) - Pin 36	SRef - VCA38 - Pin 1

   • Measure the resistance between:

     (+) PCM_B (C1915B) Connector, Harness Side	(-) Brake Booster Vacuum Sensor (C149) Connector, Harness Side
     VAC GND	VAC GND
     VAC SIG	VAC SIG
     VAC SNS P	VAC SNS P

   • 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:

     (+) ABS Module (C135) Connector, Harness Side	(-) ABS Module (C135) Connector, Harness Side
     SIGRTN - RCA37 (WHITE/BLUE) - Pin 45	SRef - VCA38 - Pin 36
     SIGRTN - RCA37 (WHITE/BLUE) - Pin 45	VREF - LCA37 - Pin 44
     SRef - VCA38 (BROWN/VIOLET) - Pin 36	VREF - LCA37 - Pin 44

   • Measure the resistance between:

     (+) PCM_B (C1915B) Connector, Harness Side	(-) PCM_B (C1915B) Connector, Harness Side
     VAC GND	VAC SIG
     VAC GND	VAC SNS P
     VAC SIG	VAC SNS P

   • Are the resistances greater than 10, 000 ohms? 

     Yes	No
     Go to  C8.	REPAIR the circuits in question.

8. C8: CHECK THE ABS MODULE OUTPUT 
   • ABS Module connector connected. (C135) Make sure the connector seats and latches correctly.
   • Ignition ON, engine OFF.
   • Measure the voltage between:

     (+) Brake Booster Vacuum Sensor (C149) Connector, Harness Side	(-)
     VREF - LCA37 (YELLOW/ORANGE) - Pin 3	Ground

   • Is the voltage approximately 4.7 volts? 

     Yes	No
     INSTALL a new brake booster vacuum sensor.	Go to  C9.

9. C9: CHECK FOR CORRECT ABS MODULE OPERATION 
   • Ignition OFF.
   • ABS Module connector disconnected. (C135)
   • Inspect all disconnected electrical connectors for the following, repair as necessary:
     • 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
   • ABS Module connector connected. (C135) Make sure the connector seats and latches correctly.
   • Brake Booster Vacuum Sensor connector connected. (C149) 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 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 actions 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.

     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. If this is a Ford paid repair, INCLUDE the RVC on the warranty claim form.

10. C10: CHECK THE ABS MODULE OUTPUT 
    • PCM_B connector connected. (C1915B) Make sure the connector seats and latches correctly.
    • Ignition ON, engine OFF.
    • Measure the voltage between:

      (+) Brake Booster Vacuum Sensor (C149) Connector, Harness Side	(-)
      VAC SNS P	Ground

    • Is the voltage approximately 4.7 volts? 

      Yes	No
      INSTALL a new brake booster vacuum sensor.	Go to  C11.

11. C11: CHECK FOR CORRECT PCM OPERATION 
    • Ignition OFF.
    • PCM_B connector disconnected. (C1915B)
    • Inspect all disconnected electrical connectors for the following, repair as necessary:
      • 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
    • PCM_B connector connected. (C1915B) Make sure the connector seats and latches correctly.
    • Brake Booster Vacuum Sensor connector connected. (C149) 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 PCM. 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 actions address this concern, INSTALL a new PCM. REFER to the "Electronic Engine Controls 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. If this is a Ford paid repair, INCLUDE the RVC on the warranty claim form.