SUBARU LEGACY 1995 Service Repair Manual

4
CHECK MISFIRE SYMPTOM.
NOTE:

Perform diagnosis according to the items listed below.

Use the MAX. misfire rate values read in step 2-4).
DTC MAX. misfire rate Next
Only one cylinder—Go to step1.
P0301 and P0302 Both rate are at 100 %, or more. Go to step
2.
P0303 and P0304 Both rate are at 100 %, or more. Go to step
3.
P0301 and P0303 Both rate are at 100 %, or more. Go to step
4.
P0302 and P0304 Both rate are at 100 %, or more. Go to step
5.
Others—Go to step
6.
1ONLY ONE CYLINDER
: Check the following items for that cylinder.

Spark plug

Spark plug cord

Fuel injector

Compression ratio

2GROUP OF #1 AND #2 CYLINDERS
: Check the following items for #1 and #2 cyl-
inders.

Spark plugs

Fuel injectors
NOTE:
If no abnormal is discovered, check for“9. F: IGNITION
SYSTEM”of #1 and #2 cylinders side.

3GROUP OF #3 AND #4 CYLINDERS
: Check the following items for #3 and #4 cyl-
inders.

Spark plugs

Fuel injectors
NOTE:
If no abnormal is discovered, check for“9. F: IGNITION
SYSTEM”of #3 and #4 cylinders side.

4GROUP OF #1 AND #3 CYLINDERS
: Check the following items for #1 and #3 cyl-
inders.

Spark plugs

Fuel injectors

Skipping timing belt teeth
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5GROUP OF #2 AND #4 CYLINDERS
: Check the following items for #2 and #4 cyl-
inders.

Spark plugs

Fuel injectors

Skipping timing belt teeth

6THE CYLINDER AT RANDOM
: Is the engine idle rough?
: Go to next. (AT models only)
: Go to DTC P0170 [T11P3], [T11P4] and [T11P5].
NOTE:
On MT models, go to DTC P0170 [T11P3], [T11P4] and
[T11P5].
OBD0631
OBD0632
: Is the differential pressure between maxi-
mum EGR system pressure (value of func-
tion mode F37) and minimum EGR system
pressure (value of function mode F38) less
than 10 mmHg?
NOTE:
Use the values read in step 3 for function modes F37 and
F38.
: Replace EGR valve.
: Go to DTC P0170 [T11P3], [T11P4] and [T11P5].
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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.
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11. Diagnostics Chart with Trouble Code

1.Check harness.


2.Check knock sensor.
3.Check knock sensor.
4.Check input signal for ECM.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.

WIRING DIAGRAM:
OBD0285

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11. Diagnostics Chart with Trouble Code

OBD0716A
1
CHECK HARNESS.
1) Turn ignition switch to OFF.
2) Disconnect connector from ECM.
3) Measure resistance between ECM harness connector
and body.
: Connector & terminal
(B84) No. 30—Body/700 kΩ, or more
: Go to step 2.
: Go to next.
OBD0716A
: Connector & terminal
(B84) No. 30—Body/400 kΩ, or less
: Go to step 3.
: Go to step 4.
B2M0244A
2
CHECK KNOCK SENSOR.
1) Disconnect connector from knock sensor.
2) Measure voltage between knock sensor connector and
body.
: Connector & terminal
(E14) No. 1—Body/700 kΩ, or more
: Check and repair the following items.

Open circuit of the harness between knock sen-
sor connector and ECM connector

Poor contact of the knock sensor connector

Poor contact of coupling connector (B21)
: Go to next.
: Check for secure tightening of the knock
sensor installation bolts.
: Tighten knock sensor installation bolts securely.
: Replace knock sensor.
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OBD0717A
3
CHECK KNOCK SENSOR.
1) Disconnect connector from knock sensor.
2) Measure resistance of harness between knock sensor
connector and body.
: Connector & terminal
(E14) No. 1—Body/400 kΩ, or less
: Replace knock sensor.
: Repair short circuit of harness between knock
sensor connector and ECM connector.
NOTE:
The harness between both connectors is shielded. Repair
short circuit of harness together with shield.
B2M0625A
4
CHECK INPUT SIGNAL FOR ECM.
1) Connect connectors to ECM and knock sensor.
2) Turn ignition switch to ON.
3) Measure voltage between ECM and body.
: Connector & terminal
(B84) No. 30—Body/2 V, or more
: Repair poor contact in ECM connector.
: Even if MIL lights up, the circuit has returned to a
normal condition at this time. (However, the pos-
sibility of poor contact still remains.)
Check and repair the following connectors.

Knock sensor connector

ECM connector

Coupling connector (B21)
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OBD0292
Z: DTC P0335
—CRANKSHAFT POSITION SENSOR
CIRCUIT MALFUNCTION (CRANK)—
OBD0293A
DESCRIPTION:

The crankshaft position sensor is installed on the oil
pump, located in the front center portion of the cylinder
block, to detect the crankshaft position. It is designed so
that the ECM accurately reads the number of pulses which
occur when protrusions provided at the perimeter of the
crankshaft sprocket (rotating together with the crankshaft)
cross the crankshaft position sensor.

The crankshaft position sensor is a molded type which
consists of a magnet, core, coil, terminals, etc.

1Terminal

2Yoke core

3Magnet

4Coil

5Core

6Cover
OBD0294A

The crankshaft sprocket is provided with six protrusions.
Crankshaft rotation causes these protrusions to cross the
crankshaft position sensor so that magnetic fluxes in the
coil change with the change in air gap between the sensor
pick-up and the sprocket. The change in air gap induces an
electromotive force which is transmitted to the ECM.
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DTC DETECTING CONDITION:

Immediately at fault recognition
TROUBLE SYMPTOM:

Engine stalls.

Failure of engine to start
1.Check harness.
2.Check crankshaft position sensor.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.

WIRING DIAGRAM:
OBD0295

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OBD0718A
1
CHECK HARNESS.
1) Turn ignition switch to OFF.
2) Disconnect connector from crankshaft position sensor.
3) Measure resistance of harness between crankshaft
position sensor connector and body.
: Connector & terminal
(E10) No. 1—Body/100 kΩ, or more
: Check and repair the following items.

Open circuit of harness between crankshaft
position sensor connector and ECM connector

Poor contact in ECM connector

Poor contact in the coupling connector (B20)
: Go to next.
OBD0718A
: Connector & terminal
(E10) No. 1—Body/10Ω, or less
: Repair short circuit of harness between crank-
shaft position sensor connector and ECM connec-
tor.
NOTE:
The harness between both connectors is shielded. Repair
short circuit of harness together with shield.
: Go to next.
OBD0719A
: Connector & terminal
(E10) No. 2—Body/10Ω, or less
: Check and repair the following items.

Open circuit of harness between crankshaft
position sensor connector and ECM connector

Poor contact in ECM connector

Poor contact in the coupling connector (B20)
: Go to step 2.
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2
CHECK CRANKSHAFT POSITION SENSOR.
: Check for secure tightening of the installa-
tion bolts of the crankshaft position sensor.
: Tighten securely.
: Go to the next step.
G2M0639
1) Remove crankshaft position sensor.
2) Measure resistance between connector terminals of
crankshaft position sensor.
: Terminals
No. 1—No. 2/1—4kΩ
: Repair poor contact in crankshaft position sensor
connector.
: Replace crankshaft position sensor.
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11. Diagnostics Chart with Trouble Code