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Electrical Systems Operation & Diagnosis Module
(602)
Introduction
This module will provide information and hands on experience that will provide you with an
understanding of Subaru Electrical System Operation and Diagnosis.
Classroom and lab participation is encouraged so that you may gain the experience needed to
repair Subaru electrical Systems on your first attempt correctly and in a timely manner.
LAN/CAN Introduction
LAN/CAN systems first appeared on the 2005 Legacy vehicles and were phased into new
generations of all existing models. Any new model introduced from 2005 was equipped with LAN/
CAN. The LAN (Local Area Network), a system where multiple computers are linked together with
a single pair of twisted wires, improves equipment operation and functions while reducing the
weight of the vehicle by eliminating a considerable amount of wiring harnesses. LAN (Bus) is a
type of computer network topology or wiring that connects all computers of a system or device.
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LAN Topologies
LAN BUS configuration allows communications between computers to continue if one of the other
members of the LAN drops out or malfunctions.
The LAN operates using Controller Area Network (CAN) communications protocol. CAN
communications are frames of vehicle data that deliver and share all vehicle information among
the computers of the LAN. The frames of data are composed of binary code or 0s and 1s that are
coded and decoded by the LAN. The voltage values that represent the 0s and 1s varies depending
on the type of CAN. Two types of CAN will be reviewed in this section of the reference booklet,
the High speed and Low speed CAN. The first LAN/CAN system equipped on Subaru vehicles
was a combination of the High speed and Low speed CAN. As the years progressed a switch to
High speed CAN only was employed.
June 2013
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