Subaru Legacy 2004 Service Manual page 1394

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
4 CHECK FUEL PRESSURE.
After connecting the pressure regulator vac-
uum hose, measure fuel pressure.
Warning:
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 out of specification as measured at this
step, check or replace pressure regulator and
pressure regulator vacuum hose.
5 CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Start the engine and warm-up completely.
2) Read the data of engine coolant tempera-
ture sensor signal using Subaru Select Moni-
tor.
NOTE:
For detailed operation procedure, refer to
"READ CURRENT DATA SHOWN ON DIS-
PLAY FOR
EN(H4DOTC)(diag)-21, Subaru Select Moni-
tor.>
6 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start and warm-up the engine until engine
coolant temperature is greater than 60!C
(140!F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all accessory switches to OFF.
5) Read the data of mass air flow and intake
air temperature sensor signal using Subaru
Select Monitor.
NOTE:
For detailed operation procedure, refer to
"READ CURRENT DATA SHOWN ON DIS-
PLAY FOR
EN(H4DOTC)(diag)-21, Subaru Select Moni-
tor.>
ENGINE". <Ref. to
ENGINE". <Ref. to
EN(H4DOTC)(diag)-105
Check
Is measured value 206 — 235
2
kPa (2.1 — 2.4 kg/cm , 30 —
34 psi)?
Is engine coolant temperature
more than 60!C (140!F)?
Is the measured value within
the following?
Ignition ON: 73.3 — 106.6 kPa
(550 — 800 mmHg, 21.65 —
31.50 inHg) Idling: 24.0 — 41.3
kPa (180 — 310 mmHg, 7.09
— 12.20 inHg)
ENGINE (DIAGNOSTICS)
Yes
Go to step 5. Repair the follow-
ing items.
Fuel pressure is
too high:
• Faulty pres-
sure regulator
• Clogged fuel
return line or
bent hose
Fuel pressure is
too low:
• Faulty pres-
sure regulator
• Improper fuel
pump discharge
• Clogged fuel
supply line
Go to step 6. Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(H4DOTC)-23,
Engine Coolant
Temperature Sen-
sor.>
Go to step 7. Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(H4DOTC)-28,
Mass Air Flow and
Intake Air Temper-
ature Sensor.>
No