Visual Inspection and Diagnostic Pre-checks

Inspect the brake booster for obvious signs of a vacuum leak.
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.

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)
SRef (Signal Reference Voltage) - VCA38	36 (BROWN/VIOLET)
SIGRTN (Signal Return) - RCA37	45 (WHITE/BLUE)

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)
SRef (Signal Reference Voltage) - VCA38	1 (BROWN/VIOLET)
SIGRTN (Signal Return) - RCA37	2 (WHITE/BLUE)

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

CA1: CHECK FOR OTHER ABS MODULE DTCS

Ignition ON, engine OFF.
Carry out the ABS self-test.

Are any brake pedal position, hydraulic pressure sensor or battery voltage DTCs present in the ABS module?

Yes	No
DIAGNOSE all ABS module brake pedal position, hydraulic pressure sensor and battery voltage DTCs before diagnosing any C101A:xx DTCS.	Go to CA2.

CA2: VERIFY ALL WIRING CONNECTIONS

Ignition OFF.
ABS Module connector disconnected. (C135)
Brake Booster Vacuum Sensor connector disconnected. (C149)
Disconnect all in-line electrical connectors between the ABS module and the brake booster vacuum sensor.
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 (Hybrid/Energi) .

Are both connectors free of corrosion, pushed-out pins and deformed or enlarged contacts?

Yes	No
Go to CA3.	REPAIR the affected terminal. Refer to OEM Connector Repair Procedures (Hybrid/Energi) .

CA3: RECHECK THE ABS MODULE FOR DTCS

Connect all in-line electrical connectors between the ABS module and the brake booster vacuum sensor. Make sure they seat and latch correctly.
Brake Booster Vacuum Sensor connector connected. (C149) Make sure the connector seats and latches correctly.
ABS Module connector connected. (C135) Make sure the connector seats and latches correctly.
Ignition ON, engine OFF.
Clear the ABS DTCs.
Ignition OFF.
Start the engine and allow it to run for at least 1 minute to build up vacuum in the brake booster.
Fully and firmly, press and release the brake pedal 3 times.
Carry out the ABS self-test.

Are any C101A:xx DTCs present?

Yes	No
Go to CA4.	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.

CA4: 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
SRef - VCA38 (BROWN/VIOLET) - Pin 36	Ground
SIGRTN - RCA37 (WHITE/BLUE) - Pin 45	Ground

Is any voltage present?

Yes	No
REPAIR the circuit.	Go to CA5.

CA5: CHECK THE VACUUM SENSOR WIRING FOR A SHORT TO GROUND

Ignition OFF.

Measure the resistance between:

(+) Brake Booster Vacuum Sensor (C149) Connector, Harness Side	(-)
VREF - LCA37 (YELLOW/ORANGE) - Pin 3	Ground
SRef - VCA38 (BROWN/VIOLET) - Pin 1	Ground
SIGRTN - RCA37 (WHITE/BLUE) - Pin 2	Ground

Are the resistances greater than 10, 000 ohms?

Yes	No
Go to CA6.	REPAIR the circuit.

CA6: 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
SRef - VCA38 (BROWN/VIOLET) - Pin 36	SRef - VCA38 - Pin 1
SIGRTN - RCA37 (WHITE/BLUE) - Pin 45	SIGRTN - RCA37 - Pin 2

Are the resistances less than 3 ohms?

Yes	No
Go to CA7.	REPAIR the circuit.

CA7: CHECK THE VACUUM SENSOR WIRING FOR A SHORT TOGETHER

Measure the resistance between:

(+) Brake Booster Vacuum Sensor (C149) Connector, Harness Side	(-) Brake Booster Vacuum Sensor (C149) Connector, Harness Side
SIGRTN - RCA37 (WHITE/BLUE) - Pin 2	SRef - VCA38 - Pin 1
SIGRTN - RCA37 (WHITE/BLUE) - Pin 2	VREF - LCA37 - Pin 3
SRef - VCA38 (BROWN/VIOLET) - Pin 1	VREF - LCA37 - Pin 3

Are the resistances greater than 10, 000 ohms?

Yes	No
For DTC C101A:1C, Go to CA8. For all others, INSTALL a new Brake Booster Vacuum Sensor. REFER to Power Brake Actuation - Brake Booster (Hybrid/Energi) .	REPAIR the circuit.

CA8: CHECK THE ABS MODULE OUTPUT

Connect all in-line electrical connectors between the ABS module and the brake booster vacuum sensor.
- Make sure the connectors seat and latch correctly.
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 between 4.7 and 5.2 volts?

Yes	No
INSTALL a new Brake Booster Vacuum Sensor. REFER to Power Brake Actuation - Brake Booster (Hybrid/Energi) .	Go to CA9.

CA9: CHECK FOR CORRECT ABS MODULE OPERATION

Ignition OFF.
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 Technical Service Bulletins 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 (Hybrid/Energi) . 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 and RETURN to the PTS web site.	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. When complete, SELECT the "X" in the top right corner to CLOSE this procedure and RETURN to the PTS web site.

Yes

INSTALL a new ABS module.
CHECK OASIS for any applicable Technical Service Bulletins 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 (Hybrid/Energi) .
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 and RETURN to the PTS web site.

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.
When complete, SELECT the "X" in the top right corner to CLOSE this procedure and RETURN to the PTS web site.