Subaru Legacy 2005 Service Manual page 3532

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)
Step
1 CHECK A/C LOCK SENSOR SIGNAL.
1) Turn the ignition switch to OFF.
2) Connect the Subaru Select Monitor to data
link connector.
3) Start the engine and turn A/C to ON.
4) Read the data of A/C lock signal using Sub-
aru Select Monitor.
NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H6DO)(diag)-27, READ CURRENT
DATA FOR ENGINE. (NORMAL MODE),
OPERATION, Subaru Select Monitor.>
2 CHECK A/C LOCK SENSOR SIGNAL.
1) Start the engine and turn A/C to ON.
2) Measure the voltage between auto A/C
control module connector and chassis ground.
Connector & terminal
(B283) No. 6 (+) — Chassis ground (
3 CHECK OUTPUT OF ECM.
Measure the voltage between ECM and chas-
sis ground.
Connector & terminal
(D137) No. 17 (+) — Chassis ground (
4 CHECK A/C LOCK SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the ECM connector.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B135) No. 23 — Chassis ground:
5 CHECK A/C LOCK SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the main fuse box connector.
3) Measure the resistance between main fuse
box terminals.
Connector & terminal
(F37) No. 16 — No. 18:
6 CHECK A/C LOCK SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the A/C lock sensor connector.
3) Measure the resistance between A/C lock
sensor terminals.
Connector & terminal
(F115) No. 1 — No. 2:
7 CHECK MAIN FUSE BOX.
1) Turn the ignition switch to OFF.
2) Disconnect the connector, and measure the
resistance between main fuse box terminals.
Connector & terminal
(F37) No. 16 — (F143) No. 12:
(F37) No. 18 — (F143) No. 14:
Diagnostic Procedure for Sensors
Is the A/C lock signal ON?
Is the voltage 7 — 14 V?
−
):
Is the voltage 7 — 14 V?
−
):
Is the resistance 240 — 290
Ω?
Is the resistance 240 — 290
Ω?
Is the resistance 240 — 290
Ω?
Is the resistance less than 10
Ω?
AC(diag)-40
Check
Go to step 4.
Replace the auto
A/C control mod-
ule.
Repair the har-
ness between
ECM and auto A/C
control module.
Replace the ECM. Go to step 5.
Go to step 7.
Repair or replace
the harness
between A/C lock
sensor and main
fuse box.
Repair or replace
the harness
between A/C lock
sensor and main
fuse box.
Yes No
Go to step 2.
Go to step 3.
Replace the ECM.
Go to step 6.
Replace the A/C
compressor
assembly. (A/C
lock switch is
faulty.)
Replace the main
fuse box.