1995 SUBARU LEGACY engine

OBD0358
OBD0688A
AH: DTC P0505
—IDLE CONTROL SYSTEM MALFUNCTION
(ISC)—
DESCRIPTION:

Idle air control solenoid valve consists of an air cut valve,
duty control valve, intake air passage and a coolant pas-
sage.

Air cut valve contains a bimetallic substance which
responds to coolant temperature, and a duty control valve
which is operated by a signal sent from ECM.

When engine coolant temperature is low, air cut valve is
fully opened by the action of the bimetallic substance so
that the air flow required for low engine coolant tempera-
tures is maintained.

ECM controls duty control valve to bring the operating
engine speed as close to preset idle speed as possible.
DTC DETECTING CONDITION:

Immediately at fault recognition
TROUBLE SYMPTOM:

Erroneous idling

Engine stalls.

Engine breathing
256
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

1
CHECK AIR INTAKE SYSTEM.
1) Turn ignition switch to ON.
2) Start engine, and idle it.
3) Check intake manifold, idle air control solenoid valve
and throttle body for loose installation and gasket for
cracks.
4) Check by-pass hoses for loose connections and cracks.
5) Check vacuum hoses for disconnections.
OBD0362A
2
CHECK OUTPUT SIGNAL FROM ECM.
1) Turn ignition switch to ON.
2) Measure voltage between ECM and body.
: Connector & terminal
(B84) No. 11—Body / 3 V, or more
(B84) No. 12—Body / 3 V, or more
: Go to step 4.
: Go to the next step.
OBD0362A
3) Turn ignition switch to OFF.
4) Disconnect connector from idle air control solenoid
valve.
5) Turn ignition switch to ON.
6) Measure voltage between ECM and body.
: Connector & terminal
(B84) No. 11—Body / 10 V, or more
(B84) No. 12—Body / 10 V, or more
: Repair short circuit of harness and replace ECM.
: Go to next.
: Is there poor contact in ECM connector?
: Repair poor contact in ECM connector.
: Go to step 3.
259
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

OBD0370
AI: DTC P0506
—IDLE CONTROL SYSTEM RPM LOWER
THAN EXPECTED (ISC
—L)—
DESCRIPTION:
Refer to“AH: DTC P0505—IDLE CONTROL SYSTEM
MALFUNCTION—[T11AH0]”.
DTC DETECTING CONDITION:

Two consecutive trips with fault
TROUBLE SYMPTOM:

Engine is difficult to start.

Engine does not start.

Erroneous idling

Engine stalls.
1.Check DTC P0505 on display.
No
Ye s

Inspect DTC P0505 using“11. Diagnostics Chart
with Trouble Code [T1100]”.

In this case, it is unnecessary to inspect DTC
P0506.
2.Check air intake system.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES. [T3D0] and [T3E0].>

262
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

2
CHECK AIR INTAKE SYSTEM.
1) Turn ignition switch to ON.
2) Start engine, and idle it.
: Is clogging the by-pass line between by-
pass hose and intake duct?
: Repair the by-pass line.
: Replace idle air control solenoid valve.
263
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

OBD0371
AJ: DTC P0507
—IDLE CONTROL SYSTEM RPM HIGHER
THAN EXPECTED (ISC
—H)—
DESCRIPTION:
Refer to“AH: DTC P0505—IDLE CONTROL SYSTEM
MALFUNCTION—[T11AH0]”.
DTC DETECTING CONDITION:

Two consecutive trips with fault
TROUBLE SYMPTOM:

Engine keeps running at higher revolution than specified
idling revolution.
1.Check DTC P0505 on display.
No
Ye s

Inspect DTC P0505 using“11. Diagnostics Chart
with Trouble Code [T1100]”.

In this case, it is unnecessary to inspect DTC
P0507.
2.Check air intake system.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES. [T3D0] and [T3E0].>

264
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

2
CHECK AIR INTAKE SYSTEM.
1) Turn ignition switch to ON.
2) Start engine, and idle it.
:
Check intake manifold, idle air control
solenoid valve and throttle body for loose
installation and gasket for cracks.

Check by-pass hose for loose connection
and cracks.

Check vacuum hoses for disconnections.
: Repair air suction and leaks.
: Replace idle air control solenoid valve.
265
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

OBD0723A
4) Measure resistance between ECM harness connector
and body.
: Connector & terminal
(B84) No. 41—Body / 10Ω, or less
: Repair short circuit of harness between ECM con-
nector and data link connector.
: Repair poor contact in ECM connector and data
link connector.
OBD0376
AL: DTC P0601
—INTERNAL CONTROL MODULE MEMORY
CHECK SUM ERROR (RAM)—
DESCRIPTION:
The RAM monitors the ECM microcomputer operation.
DTC DETECTING CONDITION:

Two consecutive trips with fault
TROUBLE SYMPTOM:

Engine does not start.

Engine stalls.
1.Check DTC P0601 on display.
Ye s
Replace ECM.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES. [T3D0] and [T3E0].>

268
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

OBD0591
AN: DTC P0705
—TRANSMISSION RANGE SENSOR CIRCUIT
MALFUNCTION (RNG)—
OBD0592A
DESCRIPTION:

The inhibitor switch assures safety when starting the
engine. This switch is mounted on the right side of the
transmission case, and is operated by the range selector
lever.

When the selector lever is set to“P”or“N”, the electri-
cal circuit is connected in the inhibitor switch and the starter
circuit is energized for cracking the engine.

When the selector lever is set to“R”,“D”,“3”,“2”,or“1”
range, the electrical circuit is disconnected in the inhibitor
switch. Hence engine cranking is disabled. In the“R”
range, the back-up light circuit is completed in the switch,
and the back-up lights come on.
DTC DETECTING CONDITION:

Two consecutive trips with fault
TROUBLE SYMPTOM:

Starter does not rotate when selector lever is in“P”or
“N”range.

Starter rotates when selector lever is in“R”,“D”,“3”,“2”
or“1”range.

Engine brake is not effected when selector lever is in“3”
range.

Shift characteristics are erroneous.
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2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code