Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P0459: EVAP System (CPC) Purge Control Valve "A" Circuit High: Notes
- -
DTC detecting condition:
Detected when two consecutive driving cycles with fault occur.
Trouble symptom:
Improper idling
Wiring diagram:
Engine Electrical System Ref. to WIRING SYSTEM (IMPREZA MODEL)>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .
CAUTION:Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .
- CHECK HARNESS BETWEEN ECM AND PURGE CONTROL SOLENOID VALVE (SHORT TO POWER SUPPLY)
.
- Turn the ignition switch to OFF.
- Disconnect the connector from ECM.
- Disconnect the connector from the purge control solenoid valve.
- Turn the ignition switch to ON.
- Measure the voltage between ECM connector and chassis ground.
Connector and terminal
(E158) No. 9 (+) - Chassis ground (-):
Is the voltage 10 V or more?
Yes: Repair the short circuit to power in the harness between ECM connector and purge control solenoid valve connector.
No: Go to 2.
- CHECK PURGE CONTROL SOLENOID VALVE
.
- Turn the ignition switch to OFF.
- Measure the resistance between purge control solenoid valve terminals.
Terminals
No. 1 - No. 2:
Is the resistance less than 1 Ω?
Yes: Replace the purge control solenoid valve. Ref. to EMISSION CONTROL (AUX. EMISSION CONTROL DEVICES) (H4DO (EXCEPT FOR HEV))>PURGE CONTROL SOLENOID VALVE .
No: Repair the poor contact of ECM connector.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.