Subaru FORESTER 2001 Service Manual page 106

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
No.
1 CONNECT SUBARU SELECT MONITOR OR
THE OBD-II GENERAL SCAN TOOL, AND
READ DATA.
1) Turn ignition switch to OFF.
2) Connect Subaru Select Monitor or the
OBD-II general scan tool to data link connec-
tor.
3) Turn ignition switch to ON and Subaru
Select Monitor or the OBD-II general scan
tool switch to ON.
4) Start engine.
5) Read data of mass air flow sensor signal
using Subaru Select Monitor or OBD-II gen-
eral scan tool.
NOTE:
¼ Subaru Select Monitor
For detailed operation procedure, refer to the
"READ CURRENT DATA FOR ENGINE".
<Ref. to EN(DOHC TURBO)-36, Subaru
Select Monitor.>
¼ 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 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 voltage between ECM connector
and chassis ground while engine is idling.
4 CHECK POWER SUPPLY TO MASS AIR
FLOW SENSOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from mass air flow
sensor.
3) Turn ignition switch to ON.
4) Measure voltage between mass air flow
sensor connector and chassis ground.
Connector & terminal
(B3) No. 1 (+) — Chassis ground (−):
Step
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?
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
10V?
EN(DOHC TURBO)-105
Check Yes
Even if MIL lights
up, the circuit has
returned to a nor-
mal condition at
this time. A tem-
porary poor con-
tact of the con-
nector or harness
may be the
cause. Repair
harness or con-
nector in the
mass air flow sen-
sor.
NOTE:
In this case,
repair the follow-
ing:
¼ Open or ground
short circuit in
harness between
mass air flow sen-
sor and ECM con-
nector
¼ 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.
Engine (Diagnostics)
No
Go to step 2.
Go to step 3.
Contact your
Subaru distributor.
NOTE:
Inspection by
DTM is required,
because probable
cause is deterio-
ration of multiple
parts.
Repair open cir-
cuit between
mass air flow sen-
sor and main
relay