Subaru 602 - Open Circuit in Main Bus

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June 2013
Electrical Systems Operation & Diagnosis Module (602)
Open Circuit in Main Bus
An open circuit on the main bus can be detected by measuring the resistance between HS-CAN
High and HS-CAN Low. For example, when measuring the resistance between HS-CAN High and
HS-CAN Low at the DLC, the resistance should be 60 Ohms.
When an open circuit occurs on the main bus, the resistance becomes 120 Ohm.
In this case, communication with control modules that are connected after the open circuit becomes
disabled. In the illustration below the BIU cannot communicate with ECM, EPS, and EPB.
Main bus
Branch bus
ELECTRIC
POWER
STEERING CM
COMBINATION
METER
BODY
INTEGRATED
UNIT
STEERING
ANGLE
SENSOR
VDC CM
120Ω120Ω
TCM
DATA LINK
CONNECTOR
A/C CM
ELECTRONIC
PARKING
BRAKE CM
ECM
Open Circuit in Main Bus
RT = ____________________
1 state 0 state
Voltage CAN High _____________ _______________
Voltage CAN Low _____________ _______________
Control Modules that cannot communicate
_______ _______ ______ _______ _______ _______ ______
_______ _______ ______ _______ _______ _______ ______
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