Subaru Impreza 2003 Service Manual page 812

ENGINE (DIAGNOSTICS)
Step
1 CHECK STATUS OF MALFUNCTION INDI-
CATOR LIGHT.
1)Turn the ignition switch to OFF.
2)Disconnect the test mode connector at lower
portion of instrument panel (on driver's side).
3)Turn the ignition switch to ON.
2 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between test mode con-
nector and chassis ground.
Connector & terminal
(B75) No. 1 (+) — Chassis ground ( − − − − ):
3 CHECK HARNESS BETWEEN ECM AND
TEST MODE CONNECTOR.
1)Turn the ignition switch to OFF.
2)Disconnect the connector from ECM.
3)Measure the resistance of harness between
ECM and test mode connector.
Connector & terminal
(B135) No. 14 — (B75) No. 1:
4 CHECK POOR CONTACT.
Check poor contact in ECM connector.
5 CHECK HARNESS BETWEEN READ MEMO-
RY CONNECTOR AND CHASSIS GROUND.
1)Turn the ignition switch to OFF.
2)Disconnect the connector from ECM.
3)Measure the resistance of harness between
read memory connector and chassis ground.
Connector & terminal
(B76) No. 1 — Chassis ground:
6 CHECK POOR CONTACT.
Check poor contact in ECM connector.
MALFUNCTION INDICATOR LIGHT
Does the malfunction indicator
light come on?
Is the voltage less than 1 V?
Is the resistance less than 1
Ω?
Is there poor contact in ECM
connector?
Is the resistance less than 1
Ω?
Is there poor contact in ECM
connector?
EN(H4SOw/oOBD)-36
Check
Go to step 2.
Go to step 3.
Go to step 4.
Repair the poor
contact in ECM
connector.
Go to step 6.
Repair the poor
contact in ECM
connector.
Yes No
Repair the mal-
function indicator
light circuit. <Ref.
to EN(H4SOw/
oOBD)-32, MAL-
FUNCTION INDI-
CATOR LIGHT
DOES NOT
COME ON., Mal-
function Indicator
Light.>
Go to step 5.
Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
ECM and test
mode connector
Replace the ECM.
<Ref. to
FU(H4SOw/
oOBD)-43, Engine
Control Module
(ECM).>
Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
read memory con-
nector and chassis
ground
Replace the ECM.
<Ref. to
FU(H4SOw/
oOBD)-43, Engine
Control Module
(ECM).>