Subaru Legacy 2004 Service Manual page 843

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
6 CHECK INPUT SIGNAL FROM ECM.
1) Start and idle the engine.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 2 (+) — Chassis ground (
(B134) No. 3 (+) — Chassis ground (
7 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B134) No. 2 (+) — Chassis ground (
(B134) No. 3 (+) — Chassis ground (
8 CHECK FRONT OXYGEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between front oxy-
gen (A/F) sensor connector terminals.
Terminals
No. 4 — No. 6:
Check
Is the voltage less than 1 V?
"
):
"
):
Does the voltage change by
shaking the ECM harness and
connector while monitoring the
value of voltage meter?
"
):
"
):
Is the resistance less than 10
!?
EN(H4SO 2.5)(diag)-84
Yes
Go to step 8. Go to step 7.
Repair the poor Go to step 8.
contact in ECM
connector.
Repair the har- Replace the front
ness and connec- oxygen (A/F) sen-
tor. sor. <Ref. to
FU(H4SO 2.5)-34,
NOTE:
Front Oxygen (A/
In this case, repair
F) Sensor.>
the following:
• Open or ground
short circuit in har-
ness between front
oxygen (A/F) sen-
sor and ECM con-
nector
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
ECM connector
No