Subaru 2002 IMPREZA Service Manual page 327

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
ENGINE (DIAGNOSTICS)
Step
CONNECT SUBARU SELECT MONITOR OR
READ DATA.
1)Turn the ignition switch to OFF.
2)Connect the Subaru Select Monitor or the
OBD-ll general scan tool to data link connec-
tor.
3)Turn the ignition switch to ON and Subaru
Select Monitor or the OBD-ll 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(D0HC TURBO)-38, Subaru Select Mon
itor.>
*OBD-ll general scan tool
For detailed operation procedures, refer to the
O b - l I General Scan Tool Instruction Manual.
THE OBD-ll GENERAL SCAN TOOL, AND
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 ( - ) :
CHECK INPUT SIGNAL FOR ECM (USING
SUBARU SELECT MONITOR).
Measure the voltage between ECM connector
and chassis ground while engine is idling.
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 sen,
sor connector and chassis ground.
Connector & terminal
(B3)
No. 1 (+)
-
Chassis ground (-):
CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW SENSOR CONNECTOR.
2)Disconnect the connector from ECM.
3)Measure the resistance of harness between
ECM and mass air flow sensor connector.
-
1)Turn the ignition switch to OFF.
Connector & terminal
(B84)
NO.
13
-
(B3)
NO.
3:
(8135)
NO.
27
-
(83) NO. 4:
(B 135) NO. 19
-
(B3)
NO.
5:
Check
3
the value equal to or more
han 1.3 g/sec (0.1 72 Ib/min) or
1.3 V and equal to or less than
140 g/sec (32 Ib/min) or 4.58
I?
s the voltage less than 0.2 V?
Ioes the voltage change more
han 0.2 V by shaking harness
ind connector of ECM while
nonitoring the value with Sub-
tru select monitor?
s the voltage more than 1 OV?
s the resistance less than
l R ?
Yes
Even if MIL lights
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
harness or con-
nector in the mass
air flow sensor.
NOTE:
In this case, repaii
the following:
Open or ground
short circuit in har-
ness between
mass air flow sen-
sor and ECM con-
nector
w
Poor contact in
mass air flow sen-
sor or ECM con-
nector
Go to step 4.
Repair poor con-
tact in ECM con-
nector.
Go to step 5.
Go to step 6.
No
;o to step 2.
30 to step 3.
;ontact with SOA
distributor) ser-
lice.
\IOTE:
nspection by DTN
s required, be.
:ause probablc
:ause is deteriora
ion of multiplt
iarts.
3epair open circuil
ietween mass air
low sensor and
nain relay
3epair open circuit
ietween ECM and
nass air flow sen-
sor connector.
EN(D0HC TURBO)-IO3