Subaru Legacy 2004 Service Manual page 554

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK ANY OTHER DTC ON DISPLAY.
2 CHECK REAR OXYGEN SENSOR DATA.
1) Warm-up the engine until engine coolant
temperature is above 70!C (158!F), and lower
the engine speed rapidly from 5,000 rpm.
2) Read the data of rear oxygen sensor signal
using Subaru Select Monitor.
NOTE:
For detailed operation procedure, refer to
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H4SO 2.0)(diag)-25, Subaru Select Mon-
itor.>
3 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance in harness
between ECM and rear oxygen sensor con-
nector.
Connector & terminals
(B136) No. 19 — (B19) No. 4:
(B136) No. 18 — (B19) No. 3:
4 CHECK HARNESS BETWEEN REAR OXY-
GEN SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from rear oxygen
sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between rear oxygen
sensor harness connector and chassis ground.
Connector & terminal
(B19) No. 4 (+) — Chassis ground (
Check
Is any other DTC displayed?
Is the voltage more than 250
mV?
Is the resistance more than 3
&?
Is the voltage 0.2 — 0.5 V?
"
):
EN(H4SO 2.0)(diag)-122
Yes
Inspect the DTC Go to step 2.
using "List of Diag-
nostic Trouble
Code (DTC)".
<Ref. to EN(H4SO
2.0)(diag)-66, List
of Diagnostic Trou-
ble Code (DTC).>
NOTE:
In this case, it is
not necessary to
inspect DTC
P0138.
Go to step 5. Go to step 3.
Repair the open Go to step 4.
circuit in harness
between ECM and
rear oxygen sen-
sor connector.
Replace the rear Repair the har-
oxygen sensor. ness and connec-
<Ref. to FU(H4SO tor.
2.0)-33, Rear Oxy-
NOTE:
gen Sensor.>
In this case, repair
the following:
• Open circuit in
harness between
rear oxygen sen-
sor and ECM con-
nector
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
ECM connector
No