Subaru Impreza 2003 Service Manual page 1281

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
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 OBD-
II general scan tool to data link connector.
3)Turn the ignition switch to ON and Subaru
Select Monitor or OBD-II general scan tool
switch to ON.
4)Start the engine.
5)Read the mass air flow sensor voltage using
Subaru Select Monitor or OBD-II general scan
tool.
NOTE:
•Subaru Select Monitor
For detailed operation procedure, refer to the
"READ CURRENT DATA FOR ENGINE".
<Ref. to EN(H4DOTC)-32, Subaru Select Mon-
itor.>
•OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Instruction 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 the 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 between ECM con-
nector and mass air flow sensor connector.
Connector & terminal
(B3) No. 2 — (B136) No. 7:
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)-105
ENGINE (DIAGNOSTICS)
Yes
Even if malfunc- Go to step 2.
tion indicator light
lights up, the cir-
cuit has returned
to a normal condi-
tion at this time.
Repair the battery Go to step 3.
short of harness
between mass air
flow sensor con-
nector and ECM
connector.
Replace the mass Repair the open
air flow sen- harness between
sor.<Ref. to mass air flow sen-
FU(H4DOTC)-34, sor connector and
Mass Air Flow and ECM connector.
Intake Air Temper-
ature Sensor.>
No