Subaru LEGACY 2004 Service Manual page 487

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
23 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL MO-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Disconnect the connectors from electronic
throttle control.
4) Measure the resistance between ECM con-
nector and electronic throttle control connector.
Connector & terminals
(B137) No. 2 — (E78) No. 3:
(B137) No. 3 — (E78) No. 3:
(B137) No. 4 — (E78) No. 6:
(B137) No. 5 — (E78) No. 6:
24 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL MO-
TOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E78) No. 3 (+) — Engine ground (
(E78) No. 6 (+) — Engine ground (
25 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL MO-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E78) No. 3 — Engine ground:
(E78) No. 6 — Engine ground:
26 CHECK ELECTRONIC THROTTLE CON-
TROL MOTOR HARNESS.
Measure the resistance between electronic
throttle control connector terminals.
Connector & terminal
(E78) No. 3 — (E78) No. 6:
27 CHECK ELECTRONIC THROTTLE CON-
TROL GROUND CIRCUIT.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 1 — Chassis ground:
(B134) No. 2 — Chassis ground:
28 CHECK ELECTRONIC THROTTLE CON-
TROL.
Measure the resistance between electronic
throttle control terminals.
Terminals
No. 1 — No. 2:
Check
Is the resistance less than 1
Ω?
Is the voltage less than 10 V?
−
):
−
):
Is the resistance more than 1
MΩ?
Is the resistance more than 1
MΩ?
Is the resistance less than 10
Ω?
Is the resistance less than 5
Ω?
EN(H4SO 2.0)(diag)-198
Yes
Go to step 24. Repair the open
circuit of harness
connector.
Go to step 25. Repair the power
supply short cir-
cuit in harness
between ECM and
electronic throttle
control.
Go to step 26. Repair the short
circuit of harness.
Go to step 27. Repair the short
circuit of harness.
Go to step 28. Repair the open
circuit of harness.
Go to step 29. Replace the elec-
tronic throttle con-
trol.
No