DTC P0452 EVAP System (CPC) Pressure Sensor/Switch Circuit Low: Notes

DTC detecting condition:

Immediately at fault recognition

CAUTION:

After servicing or replacing faulty parts, perform Clear Memory Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Clear Memory Mode . and Inspection Mode Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Inspection Mode .
Use the check board when measuring the ECM terminal voltage and resistance.

Wiring diagram:

Engine Electrical System Ref. to WIRING SYSTEM>Engine Electrical System>WIRING DIAGRAM .

Fig 1: EVAP System (CPC) Pressure Sensor/Switch Circuit Low - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

CHECK CURRENT DATA.
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor or a general scan tool, read the value of [EVAP System Vapor Pressure].
  NOTE:
  - Subaru Select Monitor
    For detailed procedures, refer to "Data Monitor". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Subaru Select Monitor .
  - General scan tool
    For detailed operation procedures, refer to the general scan tool operation manual.
Is the value in [EVAP System Vapor Pressure] 34 kPa (255 mmHg, 10 inHg) or less?
- Yes: Go to 2.
- 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.
  NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
CHECK POWER SUPPLY OF LEAK CHECK VALVE ASSEMBLY.
1. Turn the ignition switch to OFF.
2. Disconnect the connector from the leak check valve assembly.
3. Turn the ignition switch to ON.
4. Measure the voltage between the leak check valve assembly connector and chassis ground.
  Connector & terminal
  
  (R400) No. 6 (+) - Chassis ground (-):
Is the voltage 4.5 V or more?
- Yes: Go to 3.
- No: repair the harness and connector.
  NOTE:
  In this case, repair the following item:
  - Open circuit in harness between ECM and the leak check valve assembly connector
  - Poor contact of ECM connector
  - Poor contact of coupling connector
CHECK HARNESS BETWEEN ECM AND LEAK CHECK VALVE ASSEMBLY CONNECTOR.
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Measure the resistance between ECM and chassis ground.
  Connector & terminal
  
  (B134) No. 15 - Chassis ground:
Is the resistance 1 MΩ or more?
- Yes: Go to 4.
- No: Repair the short circuit to ground in harness between ECM and leak check valve assembly connector.
CHECK FOR POOR CONTACT.
Check for poor contact of leak check valve assembly connector.

Is there poor contact in the leak check valve assembly connector?
- Yes: Repair the poor contact in the leak check valve assembly connector.
- No: Replace the leak check valve assembly. Ref. to EMISSION CONTROL (AUX. EMISSION CONTROL DEVICES) (H4DOTC)>Leak Check Valve Assembly .