Subaru Impreza 2003 Service Manual page 636

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK INPUT SIGNAL FOR ECM.
1)Turn the ignition switch to ON.
2)Place the shift lever in neutral.
3)Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B136) No. 21 (+) — Chassis ground ( − − − − ):
2 CHECK INPUT SIGNAL FOR ECM.
1)Place the shift lever in a position except for
neutral.
2)Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B136) No. 21 (+) — Chassis ground ( − − − − ):
3 CHECK POOR CONTACT.
Check poor contact in ECM connector.
4 CHECK NEUTRAL POSITION SWITCH.
1)Turn the ignition switch to OFF.
2)Disconnect the connector from transmission
harness.
3)Place the shift lever in neutral.
4)Measure the resistance between transmis-
sion harness and connector terminals.
Connector & terminal
(T2) No. 1 — No. 2:
5 CHECK NEUTRAL POSITION SWITCH.
1)Place the shift lever in a position except for
neutral.
2)Measure the resistance between transmis-
sion harness connector terminals.
6 CHECK HARNESS BETWEEN ECM AND
NEUTRAL POSITION SWITCH CONNEC-
TOR.
Measure the resistance between ECM and
chassis ground.
Connector & terminal
(B136) No. 21 — Chassis ground:
7 CHECK HARNESS BETWEEN ECM AND
NEUTRAL POSITION SWITCH CONNEC-
TOR.
1)Disconnect the connector from ECM.
2)Measure the resistance of harness between
ECM and transmission harness connector.
Connector & terminal
(B136) No. 21 — (B25) No. 1:
8 CHECK HARNESS BETWEEN ECM AND
NEUTRAL POSITION SWITCH CONNEC-
TOR.
Measure the resistance of harness between
transmission harness connector and engine
ground.
Connector & terminal
(B25) No. 2 — Engine ground:
9 CHECK POOR CONTACT.
Check poor contact in transmission harness
connector.
Check
Is the voltage more than 10 V? Go to step 2.
Is the voltage less than 1 V?
Is there poor contact in ECM
connector?
Is the resistance more than 1
MΩ?
Is the resistance less than 1
Ω?
Is the resistance more than 1
MΩ?
Is the resistance less than 1
Ω?
Is the resistance less than 5
Ω?
Is there poor contact in trans-
mission harness connector?
EN(H4SO)-224
Yes
Go to step 4.
Go to step 3. Go to step 4.
Repair poor con- Contact with SUB-
tact in ECM con- ARU distributor
nector. service.
Go to step 5. Repair short circuit
in transmission
harness or replace
neutral position
switch.
Go to step 6. Repair short circuit
in transmission
harness or replace
neutral position
switch.
Go to step 7. Repair ground
short circuit in har-
ness between
ECM and trans-
mission harness
connector.
Go to step 8. Repair open circuit
in harness
between ECM and
transmission har-
ness connector.
Go to step 9. Repair open circuit
between transmis-
sion harness con-
nector and engine
ground terminal.
Repair poor con- Contact with SUB-
tact in transmis- ARU distributor
sion harness service.
connector.
No