Subaru Legacy 2003 Service Manual page 561

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
ENGINE (DIAGNOSTICS)
AB:DTC P0172 — SYSTEM TOO RICH (BANK 1) —
• DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• TROUBLE SYMPTOM:
• Erroneous idling
• Engine stalls.
• Poor driving performance
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode<Ref. to EN(H4SO)-47, OPER-
ATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO)-40, OPERATION, Inspection
Mode.> .
1 CHECK ANY OTHER DTC ON DISPLAY.
Is any other DTC displayed?
2 CHECK EXHAUST SYSTEM.
Are there holes or loose bolts on exhaust sys-
tem?
3 CHECK EGR VALVE.
Is EGR valve clogged?
4 CHECK AIR INTAKE SYSTEM.
Are there holes, loose bolts or disconnection of
hose on air intake system?
5 CHECK PURGE CONTROL SOLENOID
VALVE.
Is purge control solenoid valve clogged?
6 CHECK PCV VALVE.
Is PCV valve clogged?
Step
EN(H4SO)-164
Value
DTC indicated.
There are holes or loose bolts
on exhaust system.
EGR valve is clogged.
There are holes, loose bolts or
disconnection of hose on air
intake system.
Purge control solenoid valve is
clogged.
PCV valve is clogged.
Yes
Inspect the rele- Go to step 2.
vant DTC using
"List of Diagnostic
Trouble Code
(DTC)". <Ref. to
EN(H4SO)-83, List
of Diagnostic
Trouble Code
(DTC).>
Repair exhaust Go to step 3.
system.
Replace EGR Go to step 4.
valve.
Repair air intake Go to step 5.
system.
Replace purge Go to step 6.
control solenoid
valve.
Replace PCV Go to step 7.
valve.
No