Subaru Legacy 2004 Service Manual page 1362

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 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 and idle the engine.
5) Read the voltage of mass air flow sensor
using Subaru Select Monitor.
NOTE:
For detailed operation procedure, refer to
"READ CURRENT DATA SHOWN ON DIS-
PLAY FOR
EN(H4DOTC)(diag)-21, Subaru Select Moni-
tor.>
2 CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW SENSOR CONNECTOR.
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. 3 (+) — Chassis ground (
3 CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM connector and mass air flow
sensor connector.
Connector & terminal
(B3) No. 2 — (B136) No. 31:
ENGINE". <Ref. to
"
):
EN(H4DOTC)(diag)-73
Check
Is the voltage 0.2 — 4.7 V?
Is the voltage more than 5 V?
Is the resistance less than 1
'?
ENGINE (DIAGNOSTICS)
Yes
Even if the mal- Go to step 2.
function indicator
light illuminates,
the circuit has
returned to a nor-
mal condition at
this time.
Repair the battery Go to step 3.
short circuit in har-
ness between
mass air flow sen-
sor connector and
ECM connector.
Replace the mass Repair the open
air flow sensor. circuit in harness
<Ref. to between mass air
FU(H4DOTC)-28, flow sensor con-
Mass Air Flow and nector and ECM
Intake Air Temper- connector.
ature Sensor.>
No