Engine control unit SUBARU LEGACY 1995 Service Owner's Manual

OBD0283
Y: DTC P0325
—KNOCK SENSOR CIRCUIT MALFUNCTION
(KNOCK)—
OBD0284A
DESCRIPTION:
The knock sensor senses engine knocks and send a volt-
age signal to the ECM depending on the degree of the
knock.
This signal information is used for spark timing learning
control to provide optimal spark timing.
The knock sensor is bolted to the cylinder block at #4 pis-
ton. It senses knocks which can occur in any cylinder. Its
components are a weight, which moves up and down when
it senses vibrations, a piezo element, which produces a
voltage, and a resistor, which senses a broken circuit (all
these are molded into a single unit). When the sensor
senses engine knocks, knocking vibration is conveyed to
the weight. The up or down movement of the weight is
applied to the piezo element as a pressure difference. The
knock sensor will then produce a voltage signal in relation
to the degree of the knock.
DTC DETECTING CONDITION:

Immediately at fault recognition
TROUBLE SYMPTOM:

Poor driving performance

Knocking occurs.
217
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

B: LIST OF OUTPUT MODES
1. FUNCTION MODE
Mode Contents Abbr. Unit Contents of display Page
F00 Mode display——AT or EGI mode (when monitor is connected.) 61
F01 Battery voltage VB V Battery voltage applied to control unit. 61
F02 Vehicle speed sensor 1 VSP1 m/h Vehicle speed (miles/h) sent from vehicle speed sensor 1. 62
F03 Vehicle speed sensor 1 VSP1 km/h Vehicle speed (km/h) sent from vehicle speed sensor 1. 62
F04 Vehicle speed sensor 2 VSP2 m/h Vehicle speed (miles/h) sent from vehicle speed sensor 2. 62
F05 Vehicle speed sensor 2 VSP2 km/h Vehicle speed (km/h) sent from vehicle speed sensor 2. 62
F06 Engine speed EREV rpm Engine speed sent from ECM. 63
F07 ATF temperature sensor ATFT°F ATF temperature (°F) sent from ATF temperature sensor. 63
F08 ATF temperature sensor ATFT°C ATF temperature (°C) sent from ATF temperature sensor. 63
F09 Throttle position sensor THV V Voltage sent from throttle position sensor. 64
F10 Gear position GEAR—Transmission gear position 64
F11 Line pressure duty PLDTY % Duty ratio flowing through duty solenoid A. 65
F12 Lock-up duty LUDTY % Duty ratio flowing through duty solenoid B. 66
F13 AWD duty 4WDTY % Duty ratio flowing through duty solenoid C. 67
F14Throttle position sensor
power supplyTHVCC V Power supply voltage to throttle position sensor 68
F15 Mass air flow signal AFM V Output voltage from air flow sensor 68
56
3-2AUTOMATIC TRANSMISSION AND DIFFERENTIAL
8. Diagnostic Chart with Select Monitor

5. Control Module I/O Signal
1. I/O SIGNAL VOLTAGE
G4M0685
ContentsTerminal
No.Ignition
switch ON,
engine
OFFInput/output signals
Measured value Measuring conditions
A.B.S.
sensorFront left wheel 22
0 V 0.12—1V
No. 22—No. 4
(When it is 10 Hz.)
GND 4
Front right wheel 23
0 V 0.12—1V
No. 23—No. 21
(When it is 10 Hz.)
GND 21
Rear left wheel 8
0 V 0.12—1V
No. 8—No. 9
(When it is 10 Hz.)
GND 9
Rear right wheel 24
0 V 0.12—1V
No. 24—No. 26
(When it is 10 Hz.)
GND 26
G sensor (AWD MT model) 13 10—12 V 0 V When slanting about 14°—21.3°(θ)
Diagnosis connector30
—— —
31
Stop light switch 25 0 V 10—12 V When brake pedal is depressed.
Motor monitoring 14 0 V 10—12 V When motor operates.
Valve power supply monitoring 32 10—12 V 10—12 V Ignition switch ON*1
Hydraulic
control
unitSolenoidFront left
wheel210—12 V 0 V
When solenoid is energized to
produce output. Front right
wheel35 10—12 V 0 V
Rear wheel 18 10—12 V 0 V
Valve relay coil 27 0 V 0 V Ignition switch ON*2
Motor relay coil 28 10—12 V 0 VWhen motor operates to produce
output.
Warning light 29 10—12 V 10—12 V Ignition switch ON*3
Power
supplyIgnition 1 10—12 V 10—12 V Ignition switch ON
Relay coil (valve,
motor, etc.)17 10—12 V 10—12 V Ignition switch ON
Grounding line10 0V 0V—
20 0V 0V—
34 0V 0V—
*1: When ignition switch is OFF or the A.B.S. system is inactive: 0 V
*2: When ignition switch is OFF or the A.B.S. system is inactive: 10—12 V
*3: When ignition switch is OFF or the A.B.S. system is inactive, or during 1.5 seconds from ignition switch ON: 0 V
5
4-4aBRAKES
5. Control Module I/O Signal

3. Electrical Components Location
B4M0373A
1Hydraulic control unit

2Engine control module

3AT control module

4TCS warning light

5ABS warning light

6Diagnosis connector

7TCS operating indicator light

8TCS OFF indicator light
9TCS OFF switch

10Data link connector (for Subaru select monitor)

11Data link connector (for Subaru select monitor and OBD-II
general scan tool)

12Tone wheel

13ABS sensor

14Stroke sensor

15ABS/TCS control module
4
4-4bBRAKES
3. Electrical Components Location

4. Schematic
B4M0380A
1Hydraulic control unit

2Valve relay

3Motor relay

4Motor

5Motor sensor

6Front left inlet solenoid valve

7Front left outlet solenoid valve

8Rear right inlet solenoid valve

9Rear right outlet solenoid valve

10TCS solenoid valve 2

11Front right inlet solenoid valve

12Front right outlet solenoid valve

13Rear left inlet solenoid valve
14Rear left outlet solenoid valve

15TCS solenoid valve 1

16Pressure switch

17Data link connector

18ABS/TCS control module

19ABS warning light

20TCS operating indicator light

21TCS OFF indicator light

22TCS warning light

23Stroke sensor

24TCS OFF switch

25Diagnosis connector
26Engine control module

27Rear right ABS sensor

28Front right ABS sensor

29Front left ABS sensor

30Rear left ABS sensor

31Brake warning light

32Parking brake switch

33Brake fluid level sensor

34Generator

35Stop lamp switch

36Stop lamp

37AT control module
6
4-4bBRAKES
4. Schematic

Contents Connector No. Terminal No.Input/Output signals
Measured value and measuring conditions
TCS
control
unit ECM
commun-
icationTCS,ECM communication
(torque command)P6 14—GNDLess than 0.7 V when the vehicle stands
still.
TCS,ECM communication
(torque command)P6 5—GNDLess than 5 V when the vehicle stands
still.
TCS,ECM communication
(TCS operates)P6 12—GND4—5.4 V when TCS controls no
operations. Less than 0.7 V when it
controls operations.
ECM,TCS communication
(engine control)P6 4—GNDH/L toggle signal with the accelerator
pedal off (Cycle 20 mS, H: 10—14 V, L:
less than 0.7 V). Less than 2.0 V with the
accelerator pedal depressed. Also when
TCS OFF indicator light comes on by TCS
OFF switch.
ABS operation signal P6 13—GND10—14 V when the ABS control does not
operate still and less than 0.7 V when
ABS operates.
Fluid level sensor P7 20—GNDLess than2VwhenIGNisONand10—
14 V when idling.
Select
monitorData is received. P7 9—GND 4—4.5 V when no data is received.
Data is sent. P7 19—GND 4—4.5 V when no data is sent.
Diagnosis connector P7 8—GND 10—14 V when IGN is ON.
Power
supplyIgnition P5 1—GND 10—14 V when IGN is ON.
Battery P5 4—GND 10—14 V
Grounding
linePower P5 5—body 1Ωor less
Digital P7 15—body 1Ωor less
Power P4 6—body 1Ωor less
8
4-4bBRAKES
5. Control Module I/O Signal

8. Diagnostics Chart with Trouble Code
A: LIST OF TROUBLE CODE
Trouble code Contents of diagnosis Ref. to 4-4b
11Start code

Trouble code is shown after start code.

Only start code is shown in normal condition.—
21
Faulty ABS sensor
(Open circuit or short circuit)Front right wheel speed sensor
[T8B0] 23 Front left wheel speed sensor
25 Rear right wheel speed sensor
27 Rear left wheel speed sensor
22
Faulty ABS sensor
(Faulty ABS sensor signal)Front right wheel speed sensor
[T8C0] 24 Front left wheel speed sensor
26 Rear right wheel speed sensor
28 Rear left wheel speed sensor
31
Faulty solenoid valve circuit(s) in hydraulic
unitFront right inlet valve [T8D0]
32 Front right outlet valve [T8E0]
33 Front left inlet valve [T8D0]
34 Front left outlet valve [T8E0]
35 Rear right inlet valve [T8D0]
36 Rear right outlet valve [T8E0]
37 Rear left inlet valve [T8D0]
38 Rear left outlet valve [T8E0]
41 Faulty ABS/TCS control module [T8F0]
42 Source voltage is high.[T8G0]
43 Faulty engine control module communication cables [T8H0]
51 Faulty valve relay[T8I0]
52 Faulty motor, motor sensor and/or motor relay [T8J0]
54 Faulty stroke sensor and/or stop light switch [T8K0]
57 Faulty fluid level sensor[T8L0]
58 Faulty pressure switch[T8M0]
61
Faulty solenoid valve circuit(s) in hydraulic
unitTCS 1 valve [T8D0]
62 TCS 2 valve [T8D0]
35
4-4bBRAKES
8. Diagnostics Chart with Trouble Code

5. CHECK SOURCES OF SIGNAL NOISE.
1) Check that the mobile phone, personal radio and other
wireless apparatus are correctly installed.
2) Check that the antenna and other possible noise
sources are distant enough from the sensor harness.
3) Check that the sealed wires of the front harness sensor
(in the engine room) are securely grounded.
4) Check that between ABS/TCS control module and the
rear sensor harness has the correct twist pitch.
Twist pitch:
25 mm (0.98 in) or less
6. CHECK HYDRAULIC UNIT OPERATIONS.
1) Operate the ABS sequence control and check that the
brake fluid pressure at the malfunctioning brake line
increases and decreases properly.
45
4-4bBRAKES
8. Diagnostics Chart with Trouble Code

11. General Diagnostics Table
: Primary expected causes: Secondary expected causes
Trouble conditions
SymptomsHydraulic
unit
Speed sensor
P valve
Master cylinder
Calipers and piston
Pad
Rotor
Hand brake
Piping
Mixture of air
Brake booster and check valve
Axle and wheel
Alignment
Play of pedal
Rough road surface
Semicylindrical road surface
Loose or worn suspension
Tire
Wrong connection and wiring
Stroke sensor Solenoid valve
Motor
Mount bush ABS function
Directional stability cannot be
obtained when braking.Vehicle turns to right or left. 
Vehicle spins.
Out-of-order brakesLong braking distance
 
Brakes lock.  
Brakes drag.
Long pedal stroke  
Abnormal vehicle pitching 
Unstable braking force. One-
side brake refuses to work. 
TCS function
When accelerating abruptly,
directional stability cannot be
obtained when traveling on a
slippery road surface.Vehicle moves unsteadily.
Handle refuses to work.
Handle loses control. 
Bad acceleration, engine stall-
ing (In addition to the causes
listed here, check the ECM
specifications.)Engine stalls. Engine speed
fails to increase.
Engine speed increases sud-
denly.
Vibration occurs and abnormal
noise is produced.

When applying brakes abruptly.

When accelerating abruptly.

When driving on a slippery
road surface.Brake pedal heavily vibrates
when applying brakes.
   
Loud hydraulic unit operating
noise
Noise is produced from front
of vehicle.
Noise is produced from rear of
vehicle.
NOTE:
This list includes no engine failure and transmission failure.
127
4-4bBRAKES
11. General Diagnostics Table

No. Load
MB-1 Fuse holder (Rear power supply)
MB-2 Power window circuit breaker
MB-3Engine control module
Fuel pump relay
Main relay
OBD-II service connector
MB-4 A/C relay holder
MB-5 Headlight alarm relay (with security)
MB-6 Headlight LH
MB-7Combination meter
Daytime running light control module
Diode (Lighting)
Diode (Security)
Lighting switch
Luggage room light
Room light
Step light
Trunk room light
MB-8Combination meter
Front fog light switch
Headlight RH
MB-9Door lock timer
Headlight alarm relay
Interrupt relay
Radio
Security control module
Security indicator light
Spot light
MB-10 A/C relay holder
SBF-6Hydraulic unit (A.B.S.)
T.C.S. motor relay
SBF-7 T.C.S. valve relay
ALT-1Combination meter
Daytime running light control module
IG Headlight alarm relay
STCruise control module
Engine control module
Inhibitor switch (AT)
Interrupt relay
Starter interlock relay (MT)
FB-1Front washer motor
Rear washer motor
FB-2 Diode (A/C)
FB-3Sub fan motor
Sub fan relay-2
FB-4Engine control module
Fuel pump relay
Transmission control module
FB-5 Hydraulic unit (A.B.S.)
FB-6Front clearance light LH
Front clearance light RH
Side marker light LH
Side marker light RHNo. Load
FB-7 Door lock timer
FB-9 Hazard switch
FB-10AT shift lock control module
Key warning switch
Power antenna
FB-11 Radio
FB-12 Cigarette lighter
FB-13Remote control rearview mirror switch
Security control module
Vanity mirror illumination light
FB-14AT shift lock control module
Combination switch
Front wiper motor
Rear wiper motor
Rear wiper relay
FB-15A.B.S./T.C.S. control module
Transmission control module
FB-16Rear defogger
Rear defogger condenser
Rear defogger switch
FB-17 Rear defogger switch
FB-18AT shift lock control module
Back-up light switch (MT)
Inhibitor switch (AT)
FB-19 Hazard switch
FB-20A/C switch
Combination meter
Mode control panel
T.C.S. off switch
FB-21 Combination meter (Airbag)
FB-22Blower motor relay
Check connector
Daytime running light control module
Daytime running light relay
FRESH/RECIRC actuator
Hi-beam relay
Power window and sunroof relay
Seat belt timer
FB-23 Airbag control module
FB-24 Airbag control module
FB-25 Lighting switch
FB-26 Parking switch
FB-27 Parking switch
FB-28 Illumination light
FB-29 Illumination light
FB-30Pedal stroke sensor
Stop light switch
Stop & brake switch
FB-31 Horn relay
FB-32 Blower motor relay
FB-33 Parking switch
20
6-3WIRING DIAGRAM
6. Wiring Diagram