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Diagnostic Trouble Code (DTC) Detecting Criteria (H4SO): Overview Subaru Forester SH

Testing & Diagnostics 5 illustrations ~264 words

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.

Scheme 72

Scheme 72: COMPONENT DESCRIPTION

Valve Operation and Air Flow

In the figure below, divided by the diaphragm, the part above X is charged with atmospheric air pressure, and the part below X is charged with tank pressure. Also, the part above Y is charged with tank pressure, and the part below Y is charged with canister pressure.

If the atmospheric air pressure port is A, tank pressure port is B, and canister pressure port is C, the air flows according to pressure difference from each port as shown in the table below.

Scheme 73

Scheme 73: Valve Operation and Air Flow
Condition of pressureFlow
A < B (solenoid OFF)B --> C
B < C (solenoid OFF)C --> B
Solenoid ONB <-- --> C

AIR PRESSURE SPECIFICATION

Scheme 74

Scheme 74: When A < B (solenoid OFF)

Scheme 75

Scheme 75: When B < C (solenoid OFF)

Scheme 76

Scheme 76: When Solenoid is ON

Vehicle speed signals are taken in to the ABS control module and hydraulic control unit, and normal/erroneous data of the ABS wheel speed sensor is received by CAN communication from the ABS control module and hydraulic control unit.

ECM, TCM, VDC CM and body integrated unit are connected by high speed CAN.

(Common Specifications)

CAN Protocol 2.0 B (Active)

Frame Format: 11 Bit ID Frame (Standard Frame)

(High speed CAN)

Conforms to ISO11898

Communication Speed: 500 kbps

The barometric pressure sensor is built into the ECM.

The barometric pressure sensor is built into the ECM.

The barometric pressure sensor is built into the ECM.