Subaru 2002 IMPREZA Service Manual page 1257

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 the OBD-II general scan tool
switch to ON.
4)Start the engine.
5)Read the data of mass air flow sensor signal
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(TURBO)-34, Subaru Select Moni-
tor.>
•OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Instruction Manual.
2 CHECK INPUT SIGNAL FOR ECM.
Measure the voltage between ECM connector
and chassis ground while engine is idling.
Connector & terminal
(B84) No. 13 (+) — Chassis ground ( − − − − ):
3 CHECK INPUT SIGNAL FOR ECM (USING
SUBARU SELECT MONITOR).
Measure the voltage between ECM connector
and chassis ground while engine is idling.
4 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 the voltage between mass air flow
sensor connector and chassis ground.
Connector & terminal
(B3) No. 1 (+) — Chassis ground ( − − − − ):
Check
Is the value equal to or more
than 1.3 g/sec (0.172 lb/min) or
0.3 V and equal to or less than
240 g/sec (32 lb/min) or 4.58
V?
Is the voltage less than 0.2 V? Go to step 4.
Does the voltage change more
than 0.2 V by shaking harness
and connector of ECM while
monitoring the value with
Subaru Select Monitor?
Is the voltage more than 10 V? Go to step 5.
EN(TURBO)-97
ENGINE (DIAGNOSTICS)
Yes
Even if MIL lights Go to step 2.
up, 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
the harness or
connector in the
mass air flow sen-
sor.
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 3.
Repair the poor Contact with your
contact in ECM Subaru distributor
connector. service.
NOTE:
Inspection by DTM
is required,
cause
cause is deteriora-
tion of
parts.
Repair the open
circuit between
mass air flow sen-
sor and main
relay.
No
be-
probable
multiple