Subaru Forester 2004 Service Manual page 227

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTIC)
Step
1 CHECK ELECTRONIC THROTTLE CON-
TROL RELAY.
1) Turn the ignition switch to OFF.
2) Remove the electronic throttle control relay.
3) Connect the battery to electronic throttle
control relay terminals No. 1 and No. 3.
4) Measure the resistance between electronic
throttle control relay terminals.
Terminals
No. 2 — No. 4:
2 CHECK POWER SUPPLY OF ELECTRONIC
THROTTLE CONTROL RELAY.
Measure the voltage between electronic throt-
tle control relay connector and engine ground.
Connector & terminal
(B309) No. 1 (+) — Engine ground (
(B309) No. 2 (+) — Engine ground (
3 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY.
1) Disconnect the connector from ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between electronic
throttle control relay connector and engine
ground.
Connector & terminal
(B309) No. 3 (+) — Engine ground (
4 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY.
1) Turn the ignition switch to OFF.
2) Measure the resistance between electronic
throttle control relay connector and chassis
ground.
Connector & terminal
(B309) No. 3 — Engine ground:
(B309) No. 4 — Engine ground:
5 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY.
Measure the resistance between ECM connector
and electronic throttle control relay connector.
Connector & terminal
(B135) No. 35 — (B309) No. 3:
(B137) No. 6 — (B309) No. 4:
6 CHECK SENSOR OUTPUT.
1) Connect all the connectors.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM con-
nector terminals.
Connector & terminal
(B136) No. 18 (+) — (B136) No. 35 (
4) Check the voltage change by shaking the
harness and connector of ECM, engine har-
ness connector and electronic throttle control
connector.
Check
Is the resistance less than 1
Ω?
Is the voltage more than 5 V?
−
):
−
):
Is the voltage less than 5 V?
−
):
Is the resistance more than 1
MΩ?
Is the resistance less than 1
Ω?
Is the voltage more than 0.4 V? Go to step 7.
−
):
EN(H4DOTC 2.5)-226
Yes
Go to step 2. Replace the elec-
tronic throttle con-
trol relay.
Go to step 3. Repair open or
ground short cir-
cuit of power sup-
ply circuit.
Go to step 4. Repair power sup-
ply short circuit in
harness between
ECM and electronic
throttle control.
Go to step 5. Repair ground
short circuit in har-
ness between
ECM and elec-
tronic throttle con-
trol relay.
Go to step 6. Repair open circuit
in harness
between ECM and
electronic throttle
control relay.
Go to step 9.
No