Possible Causes

WARNING: This page is about a different car, the 2020 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

Vacuum hoses
Front hublock IWE vacuum hose connection
Brake master cylinder seal
Bent or damaged booster shell at master cylinder seal
Vacuum tube grommet
Vacuum sensor grommet

CB1: CHECK BRAKE PEDAL FEEL

Start the engine.
Press and release the brake pedal at least 3 times.

Does the brake pedal have a hard or firm feel when pressed?

Yes	No
DIAGNOSE the brake booster. REFER to BRAKE SYSTEM .	Go to CB2.

CB2: CHECK FOR OTHER ABS (ANTI-LOCK BRAKE SYSTEM) DTC (DIAGNOSTIC TROUBLE CODE)

Start the engine.
Using a diagnostic scan tool, carry out the ABS ECU Reset routine.

Are any C1015:xx or C101A:xx DTCs present?

Yes	No
Refer to Pinpoint Tests C	Go to CB3.

CB3: CHECK THE BRAKE BOOSTER AND VACUUM COMPONENTS

Ignition OFF.
Inspect the following components for signs of obvious damage:
- Brake booster
- Vacuum tube grommet
- Vacuum sensor grommet
- Brake master cylinder seal
- Booster shell at master cylinder seal
- Vacuum hoses and tubes
- Front hublock IWE vacuum hose connection

Are the components listed free from any damage?

Yes	No
Go to CB4.	INSTALL new components as necessary. Go to CB4.

CB4: TEST THE BRAKE BOOSTER

Carry out the Component Test - Brake Booster.
- Refer to BRAKE SYSTEM .

Was the component test successful?

Yes	No
Go to CB5.	INSTALL new components as directed by the component test.

CB5: CHECK THE ABS MODULE VACUUM PID

NOTE: 100mbar = 10 kPa = 3 in Hg.

NOTE: Running the engine with the vacuum sensor removed from the brake booster sets DTCs in the ABS module. Clear all DTCs once the repair is complete.

Start the engine and allow to idle for at least 20 seconds.
Access the ABS and monitor the VAC_PRS_S1 (PRESS) PID .
Read and record the PID display.
Ignition OFF.
Remove the vacuum sensor from the brake booster.
- Leave the electrical connector connected.
Connect a vacuum gauge to the vacuum sensor port.
Start the engine and allow to idle for at least 20 seconds.
Read and record the vacuum gauge display.
Ignition OFF.
Disconnect the vacuum gauge from the brake booster and install the vacuum sensor.

Does the PID display match the recorded vacuum gauge display ±10 kPa (3 inches Hg)?

Yes	No
The condition causing the concern is not present at this time. The concern may be temperature related. ALLOW the vehicle to remain outside overnight and RETEST the vacuum system.	Go to CB6.

CB6: ISOLATE THE BRAKE BOOSTER AND RETEST

Disconnect the vacuum hose from the brake booster.
Connect a vacuum gauge to the disconnected vacuum hose.
Start the engine and allow to idle for at least 20 seconds.
Read and record the vacuum gauge display.
Ignition OFF.
Disconnect the vacuum gauge from the brake booster and connect the vacuum hose.

Does the recorded vacuum gauge display match the PID display from the previous step ±10 kPa (3 inches Hg)?

Yes	No
INSTALL a new brake booster. Refer to BRAKE BOOSTER .	For Diesel Engine: Go to CB8. For all others: Go to CB7

CB7: ISOLATE THE VACUUM HOSE ASSEMBLY AND RETEST

Disconnect the vacuum hose from the intake manifold.
Connect a vacuum gauge to the intake manifold vacuum port.
Start the engine and allow to idle for at least 20 seconds.
Read and record the vacuum gauge display.
Ignition OFF.
Disconnect the vacuum gauge from the intake manifold and connect the vacuum hose.

Does the recorded vacuum gauge display match the PID display from the previous step ±10 kPa (3 inches Hg)?

Yes	No
INSTALL a new vacuum hose assembly.	CARRY OUT the Intake Manifold Vacuum Test and continue engine diagnostic. REFER to DIAGNOSIS AND TESTING .

CB8: CHECK VACUUM PUMP OPERATION

Disconnect the vacuum hose from the vacuum pump.
Connect a vacuum gauge to the vacuum pump.
Start the engine.

Does the vacuum gauge read between 51-74 kPa (15-22 in-Hg)?

Yes	No
INSTALL a new vacuum hose assembly between the vacuum pump and the brake booster.	INSTALL a new brake vacuum pump. REFER to BRAKE VACUUM PUMP - 3.0L POWER STROKE DIESEL .