Subaru 2009 IMPREZA Service Manual page 1435

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK EXHAUST SYSTEM.
Check for gas leaks or air suction caused by
loose or dislocated nuts and bolts, and open
hole at exhaust pipes.
NOTE:
Check the following positions.
• Between cylinder head and front exhaust
pipe
• Between front exhaust pipe and front catalytic
converter
• Between front catalytic converter and rear
catalytic converter
• Loose or improperly attached front oxygen
(A/F) sensor or rear oxygen sensor
2 CHECK WAVEFORM DATA ON THE SUBA-
RU SELECT MONITOR (WHILE DRIVING).
1) Drive at a constant speed between 80 —
112 km/h (50 — 70 MPH).
2) After 5 minutes have elapsed in the condi-
tion of step 1), use the Subaru Select Monitor
while still driving to read the waveform data.
• At normal condition
1
REAR OXYGEN
SENSOR VOLTAGE
(V)
0
1.5
A/F SENSOR
OUTPUT LAMBDA 1
0.5
10 sec/div
• At abnormal condition (numerous inversion)
1
REAR OXYGEN
SENSOR VOLTAGE
(V)
0
1.5
A/F SENSOR
OUTPUT LAMBDA 1
0.5
10 sec/div
Check
Is there any fault in exhaust
system?
Is a normal waveform dis-
played?
EN-06666
EN-06667
EN(H4DOTC)(diag)-214
Yes No
Repair or replace Go to step 2.
the exhaust sys-
tem. <Ref. to
EX(H4DOTC)-2,
General Descrip-
tion.>
Even if DTC is Go to step 3.
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector
may be the cause.