Subaru Forester 2004 Service Manual page 85

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTIC)
Step
1 CONNECT SUBARU SELECT MONITOR OR
THE OBD-II GENERAL SCAN TOOL, AND
READ DATA.
1) Turn the ignition switch to OFF.
2) Connect the Subaru Select Monitor or the
OBD-II general scan tool to data link connector.
3) Turn the ignition switch to ON and the Sub-
aru Select Monitor or OBD-II general scan tool
switch to ON.
4) Start the engine.
5) Connect the Subaru Select Monitor or
OBD-II general scan tool, and read the mass
air flow sensor voltage.
NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to
"READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE". <Ref. to EN(H4DOTC
2.5)-27, Subaru Select Monitor.>
• OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.
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:
Check
Is the voltage 0.2 — 4.7 V?
Is the voltage more than 5 V?
−
):
Is the resistance less than 1
Ω?
EN(H4DOTC 2.5)-84
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 battery Go to step 3.
short circuit in har-
ness between
mass air flow sen-
sor connector and
ECM connector.
Replace the mass Repair open circuit
air flow sensor. in harness
<Ref. to between mass air
FU(H4DOTC 2.5)- flow sensor con-
30, Mass Air Flow nector and ECM
and Intake Air connector.
Temperature Sen-
sor.>
No