DTC P0451: EVAP System (CPC) Pressure Sensor/Switch Circuit Range/Performance: Notes

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

1. CHECK DTC  .

   Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>DIAGNOSTIC TROUBLE CODE (DTC) .

   DTC Check 

   Is DTC P0451 displayed? (Current malfunction)

   Yes:  Go to  2.

   No:  Check the appropriate DTC using the "Diagnostic Trouble Code (DTC)". Ref. to ENGINE (DIAGNOSTICS) (H4DO)>DIAGNOSTIC TROUBLE CODE (DTC) .

2. CHECK DATA MONITOR  .
   1. Turn the ignition switch to ON (engine OFF).
   2. Using the Subaru Select Monitor or a general scan tool, read the values of [Evap System Vapor Pressure] and [Intake Manifold Absolute Pressure] to compare with actual atmospheric pressure.

      Data Monitor 

      NOTE:

      • SUBARU SELECT MONITOR For detailed operation procedures, refer to "Data Monitor". Ref. to ENGINE (DIAGNOSTICS) (H4DO)>DATA MONITOR .
      • 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 2.53 kPa (18.98 mmHg, 0.75 inHg) or more?

   Yes:  Replace the part that showed larger deviation from the actual atmospheric pressure than the other.

   • If deviations in value for [Absolute Evap Sys. Pressure] is larger: Replace the leak check valve assembly. Ref. to EMISSION CONTROL (AUX. EMISSION CONTROL DEVICES) (H4DO)>LEAK CHECK VALVE ASSEMBLY .
   • If deviations in value for [Mani. Absolute Pressure] is larger: Replace the manifold absolute pressure sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>MANIFOLD ABSOLUTE PRESSURE SENSOR .

   No:  Even if DTC is detected, the circuit has returned to a normal condition at this time.

   Reproduce the failure, and then perform the diagnosis again.

   NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.