Subaru 2009 IMPREZA Service Manual page 732

Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
2. Diagnostic Trouble Code (DTC) Detecting Criteria
A: DTC P0026 INTAKE VALVE CONTROL SOLENOID CIRCUIT RANGE/
PERFORMANCE (BANK 1)
1. OUTLINE OF DIAGNOSIS
Judge as NG with either Low NG or High NG.
A variable valve lift diagnosis oil pressure switch is installed for diagnosis. It is possible to determine whether
the intake valve is in high mode (increase the amount of lift) or in low mode (suppressing the amount of lift)
when the variable valve lift diagnosis oil pressure switch is turned ON or OFF.
• Normal
Oil switching solenoid valve duty
Large
Minimum
• Low NG
When the variable valve lift diagnosis oil pressure switch remains OFF even though the intake valve tried to
enter high mode (oil switching solenoid valve duty is large), this is judged as a Low NG.
• High NG
When the variable valve lift diagnosis oil pressure switch remains ON even though the intake valve tried to
enter low mode (oil switching solenoid valve duty is small), this is judged as a High NG.
2. COMPONENT DESCRIPTION
The variable valve lift system optimizes the intake valve lift by switching between the low lift cam and the high
lift cam according to the engine speed. The amount of intake valve lift is varied by controlling the oil switching
solenoid valve duty according to signals from the ECM.
(A) Low lift
Variable valve lift diagnosis oil
Intake valve
High mode ON
Low mode OFF
(A)
(B) High lift
GD(H4SO)-8
pressure switch
(B)
EN-05565