Subaru Legacy 2004 Service Manual page 852

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 CHECK OPTION CODE.
2 READ THE DATA CONNECTING SUBARU
SELECT MONITOR.
1) Turn the ignition switch to OFF.
2) Connect the Subaru Select Monitor to data
link connector.
3) Turn the ignition switch to ON, and the Sub-
aru Select Monitor switch to ON.
4) Start the engine.
5) Read the voltage of mass air flow sensor
using Subaru Select Monitor.
NOTE:
For detailed operation procedure, refer to the
"READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE". <Ref. to EN(H4SO
2.5)(diag)-26, Subaru Select Monitor.>
3 CHECK INPUT SIGNAL OF ECM.
Measure the voltage between ECM connector
and chassis ground while engine is idling.
Connector & terminal
(B136) No. 23 (+) — Chassis ground (
4 CHECK INPUT SIGNAL FOR ECM (USING
SUBARU SELECT MONITOR).
Measure the voltage between ECM connector
and chassis ground while engine is idling.
5 CHECK POWER SUPPLY TO MASS AIR
FLOW SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from mass air
flow sensor.
3) Turn the ignition switch to ON.
4) Measure voltage between mass air flow
sensor connector and chassis ground.
Connector & terminal
(B3) No. 1 (+) — Chassis ground (
Check
Is the option code EC, EK or
K4?
Is the voltage 0.2 — 4.7 V?
Is the voltage more than 0.2 V? Go to step 5.
"
):
Does the voltage change by
shaking the harness and con-
nector of ECM while monitor-
ing the value with Subaru
Select Monitor?
Is the voltage more than 5 V?
"
):
EN(H4SO 2.5)(diag)-93
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Refer to EN(H4SO
2.0) section. <Ref.
to EN(H4SO
2.0)(diag)-66, List
of Diagnostic Trou-
ble Code (DTC).>
NOTE:
Fuel injection sys-
tem for KA and KS
model is the same
as 2.0 L model.
Even if the mal- Go to step 3.
function indicator
light illuminates,
the circuit has
returned to a nor-
mal condition at
this time. A tempo-
rary poor contact
of the connector or
harness may be
the cause. Repair
harness or con-
nector in the mass
air flow sensor.
NOTE:
In this case, repair
the following:
• Open or ground
short circuit in har-
ness between
mass air flow sen-
sor and ECM con-
nector
• Poor contact in
mass air flow sen-
sor or ECM con-
nector
Go to step 4.
Repair the poor Replace the ECM.
contact in ECM <Ref. to FU(H4SO
connector. 2.5)-36, Engine
Control Module
(ECM).>
Go to step 6. Repair the open
circuit between
mass air flow sen-
sor and main relay
No