Subaru Legacy 2003 Service Manual page 1953

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
ENGINE (DIAGNOSTICS)
Q: DTC P0172 — SYSTEM TOO RICH (BANK 1) —
• TROUBLE SYMPTOM:
• Erroneous idling
• Engine stalls.
• Poor driving performance
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4DOSTC)-35,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOSTC)-33, Inspection
Mode.> .
1 CHECK EXHAUST SYSTEM.
Are there holes or loose bolts on exhaust sys-
tem?
2 CHECK AIR INTAKE SYSTEM.
Are there holes, loose bolts or disconnection of
hose on air intake system?
3 CHECK PCV VALVE.
Is PCV valve clogged?
4 CHECK FUEL PRESSURE.
Warning:
•Place "NO FIRE" signs near the working
area.
•Be careful not to spill fuel on the floor.
1) Release the fuel pressure.
(1) Disconnect the connector from fuel
pump relay.
(2) Start the engine and run it until it stalls.
(3) After the engine stalls, crank it for 5
more seconds.
(4) Turn the ignition switch to OFF.
2) Connect the connector to fuel pump relay.
3) Disconnect the fuel delivery hose from fuel
filter, and connect fuel pressure gauge.
4) Install the fuel filler cap.
5) Start the engine and idle while gear position
is neutral.
6) Measure the fuel pressure while discon-
necting pressure regulator vacuum hose
from intake manifold.
Is the measured value within the specified
value?
Warning:
Before removing the fuel pressure gauge,
release fuel pressure.
NOTE:
If the fuel pressure does not increase, squeeze
fuel return hose 2 to 3 times, then measure fuel
pressure again.
Step
EN(H4DOSTC)-114
Value
There is no problem.
There is no problem.
PCV valve is not clogged.
284 — 314 kPa (2.9 — 3.2 kg/
2
cm , 41 — 46 psi)
Yes
Go to step 2. Repair the exhaust
system.
Go to step 3. Repair the air
intake system.
Go to step 4. Replace PCV
valve.
Go to step 5. Repair the follow-
ing items.
Fuel presure too
high
• Clogged fuel
return line or bent
hose
Fuel pressure too
low
• Improper fuel
pump discharge
• Clogged fuel sup-
ply line
No