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Diagnostic Trouble Code (DTC) Detecting Criteria (H4DOTC): Overview Subaru Legacy BM/BR

Testing & Diagnostics 4 illustrations ~213 words

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 168

Scheme 168: Valve Operation and Air Flow
Condition of pressureFlow
A < B (solenoid OFF)B --> C
B < C (solenoid OFF)C --> B
Solenoid ONB <-- --> C

SOLENOID FUNCTION CHART

Scheme 169

Scheme 169: When A < B (solenoid OFF)

Scheme 170

Scheme 170: When B < C (solenoid OFF)

Scheme 171

Scheme 171: When Solenoid is ON

COMPONENT DESCRIPTION

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

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.

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 IS011898

Communication Speed: 500 kbps