Subaru 2002 IMPREZA Service Manual page 588

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
ENGINE (DIAGNOSTICS)
Y: DTC P0170 — FUEL TRIM MALFUNCTION —
• 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-49, OPERATION,
Clear Memory Mode.> and Inspection Mode <Ref. to EN-42, OPERATION, Inspection Mode.> .
Step
1 CHECK EXHAUST SYSTEM.
2 CHECK AIR INTAKE SYSTEM.
3 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 disconnect-
ing pressure regulator vacuum hose from
intake manifold.
Warning:
Before removing the fuel pressure gauge,
release the fuel pressure.
NOTE:
If the fuel pressure does not increase, squeeze
the fuel return hose 2 to 3 times, then measure
fuel pressure again.
Check
Are there holes or loose bolts
on exhaust system?
Are there holes, loose bolts or
disconnection of hose on air
intake system?
Is the fuel pressure between
284 — 314 kPa (2.9 — 3.2
2
kg/cm , 41 — 46 psi)?
EN-156
Yes
Repair the exhaust Go to step 2.
system.
Repair the air Go to step 3.
intake system.
Go to step 4. Repair the follow-
ing items.
Fuel pressure too
high:
• Clogged fuel
return line or
bent hose
Fuel pressure too
low:
• Clogged fuel
supply line
• Improper fuel
pump discharge
No