Subaru 2009 IMPREZA Service Manual page 1373

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AI: DTC P0172 SYSTEM TOO RICH (BANK 1)
DTC DETECTING CONDITION:
• Detected when two consecutive driving cycles with fault occur.
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-67, DTC P0172 SYSTEM TOO RICH (BANK 1), Diag-
nostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Improper idling
• Engine stalls.
• Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-54,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-43, PROCE-
DURE, Inspection Mode.>.
Step
1 CHECK EXHAUST SYSTEM.
2 CHECK AIR INTAKE SYSTEM.
3 CHECK FUEL PRESSURE.
WARNING:
Place "NO OPEN FLAMES" signs near the
working area.
CAUTION:
Be careful not to spill fuel.
Measure the fuel pressure while disconnecting
pressure regulator vacuum hose from intake
manifold. <Ref. to ME(H4DOTC)-25, INSPEC-
TION, Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze the
fuel return hose 2 to 3 times, then measure fuel
pressure again.
4 CHECK FUEL PRESSURE.
After connecting the pressure regulator vacuum
hose, measure fuel pressure. <Ref. to
ME(H4DOTC)-25, INSPECTION, Fuel Pres-
sure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
• If fuel pressure does not increase, squeeze
fuel return hose 2 to 3 times, then measure fuel
pressure again.
• If the measured value at this step is out of
specification, check or replace pressure regula-
tor and pressure regulator vacuum hose.
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 measured value 284 —
314 kPa (2.9 — 3.2 kg/cm
41 — 46 psi)?
Is the measured value 230 —
260 kPa (2.35 — 2.65 kg/cm
33 — 38 psi)?
EN(H4DOTC)(diag)-152
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-
2
, ing item.
Fuel pressure is
too high:
• Clogged fuel
return line or bent
hose
Fuel pressure is
too low:
• Improper fuel
pump discharge
• Clogged fuel
supply line
Go to step 5. Repair the follow-
2
, ing item.
Fuel pressure is
too high:
• Faulty pressure
regulator
• Clogged fuel
return line or bent
hose
Fuel pressure is
too low:
• Faulty pressure
regulator
• Improper fuel
pump discharge
• Clogged fuel
supply line
No