Subaru Legacy IV (2008 year). Manual — part 946

VDC(diag)-99

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

VEHICLE DYNAMICS CONTROL (VDC) (DIAGNOSTICS)

AZ:DTC C0074 PRESSURE SENSOR

DTC DETECTING CONDITION:
Defective pressure sensor
TROUBLE SYMPTOM:
• ABS does not operate.
• VDC does not operate.

Step

Check

Yes

No

1

CHECK STOP LIGHT SWITCH CIRCUIT.
Check stop light switch open circuit.

Is the stop light switch circuit
OK?

Go to step 2.

Repair the stop
light switch circuit.

NOTE:
If there is malfunc-
tion in the stop light
circuit, DTC may
be memorized.

2

CHECK OUTPUT OF PRESSURE SENSOR
WITH SUBARU SELECT MONITOR.
1) Select {Current Data Display & Save} in
Subaru Select Monitor.
2) Read the pressure sensor output displayed
on display.

When the brake pedal is
released, is the displayed value
–40 — 40 bar?

Go to step 3.

Replace the
VDCCM&H/U.
<Ref. to VDC-7,
VDC Control Mod-
ule and Hydraulic
Control Unit
(VDCCM&H/U).>

3

CHECK OUTPUT OF PRESSURE SENSOR
WITH SUBARU SELECT MONITOR.
1) Select {Current Data Display & Save} in
Subaru Select Monitor.
2) Read the pressure sensor output displayed
on display.

When operating the brake
pedal, does the pressure sen-
sor output value on the display
change according to the brake
pedal operation?

Go to step 4.

Replace the
VDCCM&H/U.
<Ref. to VDC-7,
VDC Control Mod-
ule and Hydraulic
Control Unit
(VDCCM&H/U).>

4

CHECK PRESSURE SENSOR.
1) Clear the memory. <Ref. to VDC(diag)-23,
Clear Memory Mode.>
2) Perform the Inspection Mode. <Ref. to
VDC(diag)-22, Inspection Mode.>
3) Read the DTC.

Is the same DTC displayed?

Replace the
VDCCM&H/U.
<Ref. to VDC-7,
VDC Control Mod-
ule and Hydraulic
Control Unit
(VDCCM&H/U).>

Go to step 5.

5

CHECK OTHER DTC DETECTION.

Is any other DTC displayed?

Perform the diag-
nosis according to
DTC. <Ref. to
VDC(diag)-34, List
of Diagnostic Trou-
ble Code (DTC).>

It results from a
temporary noise
interference.

VDC(diag)-100

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

VEHICLE DYNAMICS CONTROL (VDC) (DIAGNOSTICS)

BA:DTC C0081 SYSTEM FAILURE

DTC DETECTING CONDITION:
VDC long time sequential control
TROUBLE SYMPTOM:
• ABS does not operate.
• VDC does not operate.

Step

Check

Yes

No

1

CHECK POOR CONTACT IN CONNECTOR.

Is there poor contact in the
VDCCM& H/U and yaw rate &
lateral G sensor connector?

Repair the connec-
tor.

Go to step 2.

2

CHECK VDCCM&H/U.
1) Replace the yaw rate & lateral G sensor.
2) Connect all connectors.
3) Clear the memory. <Ref. to VDC(diag)-23,
Clear Memory Mode.>
4) Perform the Inspection Mode. <Ref. to
VDC(diag)-22, Inspection Mode.>
5) Read the DTC.

Is the same DTC displayed?

Replace the
VDCCM&H/U.

Malfunction is
found in original
yaw rate & lateral
G sensor.

VDC(diag)-101

General Diagnostic Table

VEHICLE DYNAMICS CONTROL (VDC) (DIAGNOSTICS)

13.General Diagnostic Table

A: INSPECTION

Symptom

Main probable cause

Other probable cause

Poor brake perfor-
mance

Long braking/
stopping dis-
tance

• VDCCM&H/U
• Brake pad
• Aeration to brake line
• Tire specifications, tire wear and air pressures
• Incorrect wiring or piping connections

• Defective ABS wheel speed sen-
sor or sensor gap
• Defective steering angle sensor
or improper neutral position
• Defective yaw rate & lateral G
sensor or improper installation
• Master cylinder
• Brake caliper
• Disc rotor
• Brake pipe
• Brake booster

Wheel locks.

• VDCCM&H/U
• Defective ABS wheel speed sensor or sensor gap
• Incorrect wiring or piping connections

• Defective steering angle sensor
or improper neutral position
• Defective yaw rate & lateral G
sensor or improper installation
• Brake caliper
• Brake pipe

Brake drag

• VDCCM&H/U
• Defective ABS wheel speed sensor or sensor gap
• Master cylinder
• Brake caliper
• Parking brake
• Axle and wheels
• Brake pedal play

• Defective steering angle sensor
or improper neutral position
• Defective yaw rate & lateral G
sensor or improper installation
• Brake pad
• Brake pipe

Long brake
pedal stroke

• Aeration to brake line
• Brake pedal play

• VDCCM&H/U
• Master cylinder
• Brake caliper
• Brake pad
• Brake pipe
• Brake booster

Vehicle vertical
pitching

• VDCCM&H/U
• Road surface (uneven)
• Suspension play or fatigue (reduced damping)
• Incorrect wiring or piping connections

• Defective ABS wheel speed sen-
sor or sensor gap
• Defective steering angle sensor
or improper neutral position
• Defective yaw rate & lateral G
sensor or improper installation

Poor brake perfor-
mance

Unstable or
uneven brak-
ing

• VDCCM&H/U
• Defective ABS wheel speed sensor or sensor gap
• Brake caliper
• Brake pad
• Road surface (uneven)
• Tire specifications, tire wear and air pressures
• Incorrect wiring or piping connections

• Defective ABS wheel speed sen-
sor or sensor gap
• Defective steering angle sensor
or improper neutral position
• Defective yaw rate & lateral G
sensor or improper installation
• Master cylinder
• Disc rotor
• Brake pipe
• Axle and wheels
• Road with crowns or banks
• Suspension play or fatigue
(reduced damping)

VDC(diag)-102

General Diagnostic Table

VEHICLE DYNAMICS CONTROL (VDC) (DIAGNOSTICS)

Vibration or noise
• When braking
suddenly
• When accelerat-
ing suddenly
• While driving on a
slippery road

Excessive
brake pedal
vibration

• Road surface (uneven)
• Incorrect wiring or piping connections

• VDCCM&H/U
• Brake booster
• Suspension play or fatigue
(reduced damping)

Noise from
VDCH/U

• VDCCM&H/U (mount bushing)
• Defective ABS wheel speed sensor or sensor gap
• Brake pipe

• VDCCM&H/U
• Defective steering angle sensor
or improper neutral position
• Defective yaw rate & lateral G
sensor or improper installation

Noise from the
front side of
vehicle

• VDCCM&H/U (mount bushing)
• Defective ABS wheel speed sensor or sensor gap
• Master cylinder
• Brake caliper
• Brake pad
• Disc rotor
• Brake pipe
• Brake booster
• Suspension play or fatigue (reduced damping)

• Axle and wheels
• Tire specifications, tire wear and
air pressures

Noise from the
rear side of
vehicle

• Defective ABS wheel speed sensor or sensor gap
• Brake caliper
• Brake pad
• Disc rotor
• Parking brake
• Brake pipe
• Suspension play or fatigue (reduced damping)

• Axle and wheels
• Tire specifications, tire wear and
air pressures

Engine does not accelerate or goes
into a stall when accelerating sud-
denly or driving on a slippery surface.

• VDCCM&H/U
• Defective ABS wheel speed sensor or sensor gap
• Master cylinder
• Brake caliper
• Parking brake
• Incorrect wiring or piping

• Defective steering angle sensor
or improper neutral position
• Defective yaw rate & lateral G
sensor or improper installation
• Brake pad
• Brake pipe

Poor change-direc-
tion-operation sta-
bility of TCS

Deviation to
right or left
direction

• VDCCM&H/U
• Defective ABS wheel speed sensor or sensor gap
• Defective steering angle sensor or improper neu-
tral position
• Defective yaw rate & lateral G sensor or improper
installation
• Brake caliper
• Brake pad
• Wheel alignment
• Road surface (uneven)
• Road with crowns or banks
• Tire specifications, tire wear and air pressures
• Incorrect wiring or piping connections

• Disc rotor
• Brake pipe
• Axle and wheels
• Suspension play or fatigue
(reduced damping)

Vehicle spin

• VDCCM&H/U
• Defective ABS wheel speed sensor or sensor gap
• Defective steering angle sensor or improper neu-
tral position
• Defective yaw rate & lateral G sensor or improper
installation
• Brake pad
• Tire specifications, tire wear and air pressures
• Incorrect wiring or piping connections

• Brake caliper
• Brake pipe

Symptom

Main probable cause

Other probable cause