Subaru Impreza 2004 Service Manual page 61

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 keep
the engine speed at 2,000 rpm to 3,000 rpm for
2 minutes.
2)Read the data of rear oxygen sensor signal
using Subaru Select Monitor or OBD-II general
scan tool.
NOTE:
•Subaru Select Monitor
For detailed operation procedure, refer to the
"READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE". <Ref. to
EN(H4DOTC)(diag)-32, Subaru Select Moni-
tor.>
•OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Instruction Manual.
3 CHECK REAR OXYGEN SENSOR DATA.
Read the data of rear oxygen sensor signal
using Subaru Select Monitor or OBD-II general
scan tool.
4 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1)Turn the ignition switch to OFF.
2)Disconnect the connectors from ECM and
rear oxygen sensor.
3)Measure the resistance of harness between
ECM and rear oxygen sensor connector.
Connector & terminal
LHD model
(B135) No. 17 — (B19) No. 3:
RHD model
(B135) No. 17 — (B19) No. 4:
Check
Is any other DTC displayed?
Does the value fluctuate?
Is the voltage 0.2 — 0.4 V?
Is the resistance more than 3
Ω?
EN(H4DOTC)(diag)-140
Yes
Using the List of Go to step 2.
Diagnostic Trou-
ble Code (DTC),
check the appro-
priate DTC. <Ref.
to
EN(H4DOTC)(dia
g)-74, List of Diag-
nostic Trouble
Code (DTC).>
Go to step 6. Go to step 3.
Go to step 4. Replace the rear
oxygen sensor.
<Ref. to
FU(H4DOTC)-46,
Rear Oxygen Sen-
sor.>
Repair the open Go to step 5.
circuit in harness
between ECM and
rear oxygen sen-
sor connector.
No