BVC(diag)-2
Basic Diagnostic Procedure
BRAKE VACUUM CONTROL (BVC) (DIAGNOSTICS)
1. Basic Diagnostic Procedure
A: PROCEDURE
CAUTION:
•Subaru Select Monitor is required for reading DTC, reading the current data and clearing the mem-
ory.
•Remove foreign matter (dust, water, oil, etc.) from the engine control module (ECM) connector
when removing or installing.
NOTE:
•To check the harness for broken wires or short circuits, shake problem spot or connector.
•Refer to “Check List for Interview”.
Step Check Yes No
1CHECK PRE-INSPECTION.
1) Ask the customer when and how the trou-
ble occurred using interview check list.
2) Check the error display. (Odo/trip meter)
Is “Er-bb” displayed on the
screen?
Go to step 3.Go to step 2.
2BASIC INSPECTION
Check the components which might affect the
brake vacuum control.
Is the component that might
affect the vacuum control nor-
mal?
Go to step 3.Repair or replace
each component.
3CHECK INDICATION OF DTC.
1) Turn the ignition switch to OFF.
2) Connect the Subaru Select Monitor to data
link connector.
3) Turn the ignition switch to ON, and the Sub-
aru Select Monitor power switch to ON.
4) Read the DTC.
(DTC).>
5) Record all DTC.
Is DTC displayed? Go to step 5.Go to step 4.
4PERFORM GENERAL DIAGNOSTICS.
Inspect using “General Diagnostic Table”.
Is result of inspection OK? Finish the diagno-
sis.
Go to step 5.
5PERFORM THE DIAGNOSIS.
1) Correct the cause of trouble according to
DTC.
2) Perform the clear memory mode.
Mode.>
3) Perform the inspection mode.
Mode.>
4) Read the DTC.
(DTC).>
Is DTC displayed? Repeat step 4 until
DTC is not shown.
Finish the diagno-
sis.
BVC(diag)-5
General Description
BRAKE VACUUM CONTROL (BVC) (DIAGNOSTICS)
3. General Description
A: CAUTION
1. SRS AIRBAG SYSTEM
Airbag system wiring harness is routed near the ABS wheel speed sensor and VDCCM&H/U.
CAUTION:
•All airbag system wiring harness and connectors are colored yellow. Do not use the electrical test
equipment on these circuits.
•Be careful not to damage the airbag system wiring harness.
B: INSPECTION
Before performing diagnosis, check the following items which might affect the brake vacuum control.
1. BATTERY
Measure the battery voltage and check electrolyte.
Standard voltage: 12 V or more
Specific gravity: 1.260 or more
2. BRAKE VACUUM HOSE
Make sure the brake vacuum hose is not cracked or loose.
C: PREPARATION TOOL
1. SPECIAL TOOL
2. GENERAL TOOL
ILLUSTRATION TOOL NUMBER DESCRIPTION REMARKS
18482AA010 CARTRIDGE Troubleshooting for the electrical system.
22771AA030 SUBARU SELECT
MONITOR KIT
Tr o u b l e s h o o t i n g f o r t h e e l e c t r i c a l s y s t e m .
TOOL NAME REMARKS
Circuit tester Used for measuring resistance, voltage and current.
Oscilloscope Used for measuring the sensor.
ST18482AA010
ST22771AA030
BVC(diag)-16
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
BRAKE VACUUM CONTROL (BVC) (DIAGNOSTICS)
Step Check Yes No
1CHECK BRAKE VACUUM SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the brake vacuum sensor con-
nector.
3) Remove the brake vacuum sensor.
4) Measure the resistance between brake
vacuum sensor connector terminals.
Te r m i n a l s
No. 1 — No. 3:
No. 2 — No. 3:
Is the resistance 15 kΩ or
less?
Go to step 2.Replace the brake
vacuum sensor.
Sensor.>
2CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM SENSOR CONNECTOR.
1) Disconnect the connectors from ECM.
2) Measure the resistance of the harness
between ECM and the brake vacuum sensor
connector.
Connector & terminal
(B135) No. 30 — (B411) No. 1:
(B135) No. 22 — (B411) No. 3:
(B134) No. 27 — (B411) No. 2:
Is the resistance less than 1
Ω?
Go to step 3.Repair the open
circuit of harness
between ECM and
brake vacuum
sensor connector.
3CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM SENSOR CONNECTOR.
Measure the resistance of harness between
ECM and chassis ground.
Connector & terminal
(B135) No. 30 — Chassis ground:
(B135) No. 22 — Chassis ground:
(B134) No. 27 — Chassis ground:
Is the resistance more than 1
MΩ?
Go to step 4.Repair the ground
short of the har-
ness between
ECM and brake
vacuum sensor
connector.
4CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM SENSOR CONNECTOR.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B135) No. 30 (+) — Chassis ground (–):
(B135) No. 22 (+) — Chassis ground (–):
(B134) No. 27 (+) — Chassis ground (–):
Is the voltage less than 0.5 V? Go to step 5.Repair the battery
short circuit
between ECM and
brake vacuum
sensor connector.
5CHECK THE BRAKE VACUUM SENSOR
POWER SUPPLY.
1) Connect the connectors to ECM and brake
vacuum sensor.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM con-
nector terminals.
Connector & terminal
(B135) No. 22 (+) — (B135) No. 30 (–):
Is the voltage 4.75 — 5.25 V? Go to step 6.Replace the ECM.
Engine Control
Module (ECM).>
6CHECK CURRENT DATA.
1) Turn the ignition switch to ON.
2) Depress the brake pedal several times, until
the pedal becomes firm.
3) Read the current data of the brake negative
pressure pump system using the Subaru
Select Monitor.
Is the atmospheric pressure —
brake booster pressure
between –8 — +8 mmHg?
Te m p o r a r y p o o r
contact occurs.
Replace the ECM.
Engine Control
Module (ECM).>
BVC(diag)-18
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
BRAKE VACUUM CONTROL (BVC) (DIAGNOSTICS)
Step Check Yes No
1CHECK BRAKE VACUUM HOSE.
1) Turn the ignition switch to OFF.
2) Check that status of the brake vacuum
hose connection.
Is the brake vacuum hose con-
nected firmly?
Go to step 2.Connect the brake
vacuum hose.
2CHECK BRAKE VACUUM HOSE.
1) Turn the ignition switch to ON and start
engine.
2) Check for leakage from the brake vacuum
hose.
Is there a leak from the brake
vacuum hose?
Replace the brake
vacuum hose.
Go to step 3.
3CHECK BRAKE VACUUM SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the brake vacuum sensor con-
nector.
3) Remove the brake vacuum sensor.
4) Measure the resistance between brake
vacuum sensor connector terminals.
Te r m i n a l s
No. 1 — No. 3:
No. 2 — No. 3:
Is the resistance 15 kΩ or
less?
Go to step 4.Replace the brake
vacuum sensor.
Sensor.>
4CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM SENSOR CONNECTOR.
1) Disconnect the connectors from ECM.
2) Measure the resistance of the harness
between ECM and the brake vacuum sensor
connector.
Connector & terminal
(B135) No. 30 — (B411) No. 1:
(B135) No. 22 — (B411) No. 3:
(B134) No. 27 — (B411) No. 2:
Is the resistance less than 1
Ω?
Go to step 5.Repair the open
circuit of harness
between ECM and
brake vacuum
sensor connector.
5CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM SENSOR CONNECTOR.
Measure the resistance of harness between
ECM and chassis ground.
Connector & terminal
(B135) No. 30 — Chassis ground:
(B135) No. 22 — Chassis ground:
(B134) No. 27 — Chassis ground:
Is the resistance more than 1
MΩ?
Go to step 6.Repair the ground
short circuit
between ECM and
brake vacuum
sensor connector.
6CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM SENSOR CONNECTOR.
Measure the voltage between ECM and chas-
sis ground.
Connector & terminal
(B135) No. 30 (+) — Chassis ground (–):
(B135) No. 22 (+) — Chassis ground (–):
(B134) No. 27 (+) — Chassis ground (–):
Is the voltage less than 0.5 V? Go to step 7.Repair the battery
short of the har-
ness between
ECM and brake
vacuum sensor
connector.
7CHECK THE BRAKE VACUUM SENSOR
POWER SUPPLY.
1) Connect the connectors to ECM and brake
vacuum sensor.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM con-
nector terminals.
Connector & terminal
(B135) No. 22 (+) — (B135) No. 30 (–):
Is the voltage 4.75 — 5.25 V? Go to step 8.Replace the ECM.
Engine Control
Module (ECM).>
BVC(diag)-21
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
BRAKE VACUUM CONTROL (BVC) (DIAGNOSTICS)
Step Check Yes No
1CHECK BRAKE VACUUM HOSE.
1) Turn the ignition switch to OFF.
2) Check that status of the brake vacuum
hose connection.
Is the brake vacuum hose con-
nected firmly?
Go to step 2.Connect the brake
vacuum hose.
2CHECK BRAKE VACUUM HOSE.
1) Turn the ignition switch to ON and start
engine.
2) Check for leakage from the brake vacuum
hose.
Is there a leak from the brake
vacuum hose?
Replace the brake
vacuum hose.
Go to step 3.
3CHECK BRAKE VACUUM SENSOR CON-
NECTOR.
Check that status of the brake vacuum sensor
connector connection.
Is the brake vacuum sensor
connector connected firmly?
Go to step 4.Connect the brake
vacuum sensor
connector.
4CHECK BRAKE VACUUM SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the brake vacuum sensor con-
nector.
3) Remove the brake vacuum sensor.
4) Measure the resistance between brake
vacuum sensor connector terminals.
Connector & terminal
No. 1 — No. 3:
No. 2 — No. 3:
Is the resistance 15 kΩ or
less?
Go to step 5.Replace the brake
vacuum sensor.
Sensor.>
5CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM SENSOR CONNECTOR.
1) Disconnect the connectors from ECM.
2) Measure the resistance of the harness
between ECM and the brake vacuum sensor
connector.
Connector & terminal
(B135) No. 30 — (B411) No. 1:
(B135) No. 22 — (B411) No. 3:
(B134) No. 27 — (B411) No. 2:
Is the resistance less than 1
Ω?
Go to step 6.Repair the open
circuit of harness
between ECM and
brake vacuum
sensor connector.
6CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM SENSOR CONNECTOR.
Measure the resistance of harness between
ECM and chassis ground.
Connector & terminal
(B135) No. 30 — Chassis ground:
(B135) No. 22 — Chassis ground:
(B134) No. 27 — Chassis ground:
Is the resistance more than 1
MΩ?
Go to step 7.Repair the ground
short of the har-
ness between
ECM and brake
vacuum sensor
connector.
7CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM SENSOR CONNECTOR.
Measure the voltage between ECM and chas-
sis ground.
Connector & terminal
(B135) No. 30 (+) — Chassis ground (–):
(B135) No. 22 (+) — Chassis ground (–):
(B134) No. 27 (+) — Chassis ground (–):
Is the voltage less than 0.5 V? Go to step 8.Repair the battery
short of the har-
ness between
ECM and brake
vacuum sensor
connector.
8CHECK THE BRAKE VACUUM SENSOR
POWER SUPPLY.
1) Connect the connectors to ECM and brake
vacuum sensor.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM con-
nector terminals.
Connector & terminal
(B135) No. 22 (+) — (B135) No. 30 (–):
Is the voltage 4.75 — 5.25 V? Go to step 9.Replace the ECM.
Engine Control
Module (ECM).>
BVC(diag)-24
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
BRAKE VACUUM CONTROL (BVC) (DIAGNOSTICS)
Step Check Yes No
1CHECK CONNECTOR.
Check that status of the brake vacuum sensor
and brake vacuum pump connection.
Are the brake vacuum sensor
and brake vacuum pump con-
nected firmly?
Go to step 2.Connect the con-
nector.
2CHECK FUSE.
1) Turn the ignition switch to OFF.
2) Remove the brake vacuum pump fuse.
3) Check the condition of fuse.
Is the fuse blown out? Replace the fuse. Go to step 3.
3CHECK BRAKE VACUUM PUMP RELAY.
1) Turn the ignition switch to OFF.
2) Remove the brake vacuum pump relay from
the relay box.
3) Connect the battery to terminals No. 1 and
No. 3 of the brake vacuum pump relay.
4) Measure the resistance between the brake
vacuum pump relay terminals.
Te r m i n a l s
No. 4 — No. 5:
Is the resistance less than 1
Ω?
Go to step 4.Replace the brake
vacuum pump
relay.
4CHECK BRAKE VACUUM PUMP RELAY
POWER SUPPLY.
1) Turn the ignition switch to ON.
2) Measure the voltage between brake vac-
uum pump relay connector and chassis
ground.
Connector & terminal
(VC2) No. 1 (+) — Chassis ground (–):
(VC2) No. 4 (+) — Chassis ground (–):
Is the voltage more than 10 V? Go to step 5.Repair the open or
ground short cir-
cuit of power sup-
ply circuit.
5CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM PUMP RELAY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector of ECM.
3) Measure the resistance of the harness
between ECM and the brake vacuum pump
relay connector.
Connector & terminal
(B136) No. 8 — (VC2) No. 3:
Is the resistance less than 1
Ω?
Go to step 6.Repair the open
circuit of harness
between ECM and
the brake vacuum
pump relay con-
nector.
6CHECK HARNESS BETWEEN THE BRAKE
VACUUM PUMP AND BRAKE VACUUM
PUMP RELAY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the brake vacuum pump con-
nector.
3) Measure the resistance of the harness
between the brake vacuum pump and brake
vacuum pump relay connector.
Connector & terminal
(VC2) No. 5 — (B417) No. 1:
Is the resistance less than 1
Ω?
Go to step 7.Repair the open
circuit of the har-
ness between the
brake vacuum
pump and the
brake vacuum
pump relay con-
nector.
7CHECK THE HARNESS BETWEEN ECM
AND BRAKE VACUUM PUMP CONNECTOR.
Measure the resistance of the harness
between brake vacuum pump connector and
the chassis ground.
Connector & terminal
(B417) No. 1 — Chassis ground:
Is the resistance more than 1
MΩ?
Go to step 8.Repair the ground
short of the har-
ness between
ECM and brake
vacuum pump
connector.
8CHECK THE HARNESS BETWEEN ECM
AND BRAKE VACUUM PUMP CONNECTOR.
Measure the voltage between brake vacuum
pump connector and the chassis ground.
Connector & terminal
(B417) No. 1 (+) — Chassis ground (–):
Is the voltage less than 0.5 V? Go to step 9.Repair the battery
short of the har-
ness between the
ECM and the
brake vacuum
pump connector.
BVC(diag)-27
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
BRAKE VACUUM CONTROL (BVC) (DIAGNOSTICS)
Step Check Yes No
1CHECK BRAKE VACUUM PUMP RELAY.
1) Turn the ignition switch to OFF.
2) Remove the brake vacuum pump relay from
the relay box.
3) Connect the battery to terminals No. 1 and
No. 3 of the brake vacuum pump relay.
4) Measure the resistance between the brake
vacuum pump relay terminals.
Te r m i n a l s
No. 4 — No. 5:
Is the resistance less than 1
Ω?
Go to step 2.Replace the brake
vacuum pump
relay.
2CHECK BRAKE VACUUM PUMP RELAY
POWER SUPPLY.
1) Turn the ignition switch to ON.
2) Measure the voltage between brake vac-
uum pump relay connector and chassis
ground.
Connector & terminal
(VC2) No. 1 (+) — Chassis ground (–):
(VC2) No. 4 (+) — Chassis ground (–):
Is the voltage more than 10 V? Go to step 3.Repair the open or
ground short cir-
cuit of power sup-
ply circuit.
3CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM PUMP RELAY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector of ECM.
3) Measure the resistance of the harness
between ECM and the brake vacuum pump
relay connector.
Connector & terminal
(B136) No. 8 — (VC2) No. 3:
(B135) No. 25 — (VC2) No. 5:
Is the resistance less than 1
Ω?
Go to step 4.Repair the open
circuit of harness
between ECM and
the brake vacuum
pump relay con-
nector.
4CHECK HARNESS BETWEEN THE BRAKE
VACUUM PUMP AND BRAKE VACUUM
PUMP RELAY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the brake vacuum pump con-
nector.
3) Measure the resistance of the harness
between the brake vacuum pump and brake
vacuum pump relay connector.
Connector & terminal
(VC2) No. 5 — (B417) No. 1:
Is the resistance less than 1
Ω?
Go to step 5.Repair the open
circuit of the har-
ness between the
brake vacuum
pump and the
brake vacuum
pump relay con-
nector.
5CHECK ECM.
1) Connect the brake vacuum pump relay.
2) Connect the connectors to the brake vac-
uum pump and ECM.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B136) No. 8 — Chassis ground (–):
Is the voltage more than 10 V? Replace the ECM.
Engine Control
Module (ECM).>
Te m p o r a r y p o o r
contact occurs.
BVC(diag)-29
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
BRAKE VACUUM CONTROL (BVC) (DIAGNOSTICS)
Step Check Yes No
1CHECK BRAKE VACUUM HOSE.
1) Turn the ignition switch to OFF.
2) Check that status of the brake vacuum
hose connection.
Is the brake vacuum hose con-
nected firmly?
Go to step 2.Connect the brake
vacuum hose.
2CHECK BRAKE VACUUM HOSE.
1) Turn the ignition switch to ON and start
engine.
2) Check for leakage from the brake vacuum
hose.
Is there a leak from the brake
vacuum hose?
Replace the brake
vacuum hose.
Go to step 3.
3CHECK BRAKE VACUUM PUMP RELAY.
1) Turn the ignition switch to OFF.
2) Remove the brake vacuum pump relay from
the relay box.
3) Connect the battery to terminals No. 1 and
No. 3 of the brake vacuum pump relay.
4) Measure the resistance between the brake
vacuum pump relay terminals.
Te r m i n a l s
No. 4 — No. 5:
Is the resistance less than 1
Ω?
Go to step 4.Replace the brake
vacuum pump
relay.
4CHECK BRAKE VACUUM PUMP RELAY
POWER SUPPLY.
1) Turn the ignition switch to ON.
2) Measure the voltage between brake vac-
uum pump relay connector and chassis
ground.
Connector & terminal
(VC2) No. 1 (+) — Chassis ground (–):
(VC2) No. 4 (+) — Chassis ground (–):
Is the voltage more than 10 V? Go to step 5.Repair the open or
ground short cir-
cuit of power sup-
ply circuit.
5CHECK HARNESS BETWEEN ECM AND
BRAKE VACUUM PUMP RELAY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector of ECM.
3) Measure the resistance of the harness
between ECM and the brake vacuum pump
relay connector.
Connector & terminal
(B136) No. 8 — (VC2) No. 3:
(B135) No. 25 — (VC2) No. 5:
Is the resistance less than 1
Ω?
Go to step 6.Repair the open
circuit of harness
between ECM and
the brake vacuum
pump relay con-
nector.
6CHECK HARNESS BETWEEN THE BRAKE
VACUUM PUMP AND BRAKE VACUUM
PUMP RELAY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the brake vacuum pump con-
nector.
3) Measure the resistance of the harness
between the brake vacuum pump and brake
vacuum pump relay connector.
Connector & terminal
(VC2) No. 5 — (B417) No. 1:
Is the resistance less than 1
Ω?
Go to step 7.Repair the open
circuit of the har-
ness between the
brake vacuum
pump and the
brake vacuum
pump relay con-
nector.
7CHECK ECM.
1) Connect the brake vacuum pump relay.
2) Connect the connectors to the brake vac-
uum pump and ECM.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B136) No. 8 — Chassis ground (–):
Is the voltage more than 10 V? Replace the ECM.
Engine Control
Module (ECM).>
Te m p o r a r y p o o r
contact occurs.