Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual - part 258
EN(H4DOTC)(diag)-256
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CH:DTC P0451 EVAPORATIVE EMISSION SYSTEM PRESSURE SENSOR/
SWITCH RANGE/PERFORMANCE
DTC DETECTING CONDITION:
• Detected when 2 consecutive driving cycles with fault occur.
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-155, DTC P0451 EVAPORATIVE EMISSION SYS-
TEM PRESSURE SENSOR/SWITCH RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting
Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-63,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-49, PROCE-
Step
Check
Yes
No
1
CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed?
2
CHECK CURRENT DATA.
1) Turn the ignition switch to ON (engine OFF).
2) Using the Subaru Select Monitor or general
scan tool, read the value in «Atmosphere Pres-
sure» and «Mani. Absolute Pressure», and
compare them with the actual atmospheric
pressure.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-40, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
• To read the actual atmospheric pressure,
connect the Subaru Select Monitor or general
scan tool to the other known good vehicle.
Is the difference with the actual
atmospheric pressure 3.3 kPa
(24.5 mmHg, 1 inHg) or more?
Replace the part
that showed larger
deviation from the
actual atmospheric
pressure than the
other.
• If deviations in
value for «Atmo-
sphere Pressure»
is larger: Replace
the leak check
valve assembly.
<Ref. to EC(STI)-
19, Leak Check
Valve Assembly.>
<Ref. to EC(w/o
STI)-20, Leak
Check Valve
Assembly.>
• If deviations in
value for «Mani.
Absolute Pres-
sure» is larger:
Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(STI)-43,
Manifold Absolute
Pressure Sen-
sor.> <Ref. to
FU(w/o STI)-43,
Manifold Absolute
Pressure Sensor.>
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.