automotive computer networks

8/3/2019 Automotive Computer Networks

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AUTOMOTIVE COMPUTER NETWORKS

Electrical/Electronics 3


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COMPUTER COMMUNICATION

Modules receive & send signals:

In analog & digital form.

Through data links.

Some modules transmit data in only onedirection.

Other modules can transmit data in bothdirections.


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NETWORKS

Allow:Computers to

communicate

with eachother.

Information tobe shared

betweencomputers onthe network.


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Modules that communicate with each othermay include:ABS module (Antilock Brake System)

BCM (Body Control Module)ECM (Engine Control Module)Suspension Control ModuleClimate Control Module

Cruise Control ModulePower Steering Control ModulePCM (Powertrain Control Module)


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Modules that communicate with each othermay include:

Remote Keyless Entry Module

Drivers Door Module

Drivers Seat Module

Lighting Control Module

Front Electronic Module

Rear Electronic Module


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NETWORKS

An automotive network refers to the controlmodules and wiring that allowscommunication to take place.


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NETWORKS

Provide improved diagnostic capabilities.

A scan tool is connected to the vehicles

network at the Data Link Connector (DLC).


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DATA LINK CONNECTOR

The DLC allows for:

Diagnosis of theentire network at a

single point.Monitoring system

inputs.

Controlling systemoutputs.


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DATA LINK CONNECTOR

The DLC is usually a 16-pin connectorlocated under the instrument panel.


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DATA BUS

The wires that connect the control modulesand scan tool to each other.


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BINARY CODE

Modules on a network communicate usingbinary code.

Binary code is represented as zeros andones.


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BINARY CODE

The ones usually represent a high voltagereading, typically 5, 7, or 12 volts.

The zeros usually represent a low voltagereading, typically 0 volts.


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BINARY CODE

Each 0 or 1 isreferred to as abit.

8 bits make upone byte orword.


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BINARY CODE

Modules interpret this binary code asmessages from other modules on thenetwork.


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PROTOCOL

The electroniclanguage that thenetwork uses.

Protocols usebinary numbers tospeak different

electroniclanguages.


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PROTOCOL

Different networks operate at differentspeeds.

The speed is referred to as the baud rate.


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PROTOCOL

There are manydifferent protocolsdepending on the

manufacturer.

There are somesimilarities.


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PROTOCOL

More than onenetwork may beused on the same

vehicle,depending onvehicle features.


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PROTOCOL

Most controlmodules areconnected

to onenetworkonly.


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PROTOCOL

Some modulesmay be connectedto more than one

network. These modules

must understandand speak morethan one protocol.


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MULTIPLE NETWORK EXAMPLE

The instrumentcluster module(ICM) receives

vehicle speedinformation fromthe ABS module.

Both are ondifferent networks.


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MULTIPLE NETWORK EXAMPLE

The ICMtranslates theinformationand sends it tothetemperaturecontrolmodule.

Thetemperaturecontrol moduleis on its ownnetwork.


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PROTOCOL

Scan tools: Are designed

to understandand speak

more than oneprotocol.

Cancommunicate

with severaldifferentnetworks.


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NETWORKS

Two basic Types of networks:

Diagnostic

Multiplex


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DIAGNOSTIC NETWORK

Onlycommunicates:

When ascan tool isconnected.

In onedirection.


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DIAGNOSTIC NETWORK

A single wire data bus connects the modulesto the DLC.


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DIAGNOSTIC NETWORK

The scan tool communicates with eachmodule.


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DIAGNOSTIC NETWORK

Each modulecommunicates with the

scan tool.Modules do

notcommunicat

e with eachother.


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DIAGNOSTIC NETWORK

The module can only transmit one piece ofdata at a time.


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DIAGNOSTIC NETWORK

Information is very slow.


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DIAGNOSTIC NETWORK

If a short to power or short to ground occurs,the entire network will not operate.


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DIAGNOSTIC NETWORK

If an open occurs, the scan tool cannotcommunicate with that module.

The rest of the network will operate normally.


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MULTIPLEX NETWORKS

Allows for:

Module-to-modulecommunication.

Sharing ofinformationbetween modules.

Communicationwith a scan tool(mostapplications).


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MULTIPLEX NETWORKS

Types of multiplexnetworks may include:

Single wire

Twisted wire

Audio

CAN (Controller Area

Network)


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SINGLE WIRE NETWORKS

A single communication wire is used.

Information is sent back and forth along thesame wire.


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Typically used for body and audio systemcomponents.


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Messages are sent across the data bus as aseries of 0 volt pulses.

Typically starts at 12 volts.

Pulsed to 0 volts by a module.


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If a short to power or short to ground occurs,the entire network is disabled.


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If an open occurs:

Modules after the open cannot communicate.

The rest of the network will operate normally.


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TWISTED WIRE NETWORKS

Modules on some multiplex networkscommunicate over a twisted pair of wires.


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Twisting the wires helps to reduce electricalinterference.

Data bus wires are designated as bus+ and

bus-.


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Messages are sent across the data bus asvoltage pulses.

Each pulse is one bit.


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A series of bits is recognized by the moduleas a binary message.


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Each wire carries identical messages as amirror image of each other.


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A module canread themessage from

either wire. Both circuits are

not required.


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If damageoccurs toone wire,the system

continuesto operatenormally.

A network

test willidentify thefault.


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If damage occurs to both wires, multipleconcerns will exist.

Modules depend on each other for data.


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A total loss of communication will result inmultiple DTCs from different modules on thenetwork.

Complete network failure is rare due to thetwo paths for communication.


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AUDIO NETWORKS

Some manufacturers use a networkdesigned to allow audio components tocommunicate with each other.


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AUDIO NETWORKS

These systems may:Use a twisted pair of

wires.

Include the climatecontrol system.

Include a third wire,Audio System On

(ASYSON) Incorporate a self-test

procedure.


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AUDIO NETWORKS

Self-testprocedure:

Varies between

applications.Refer to service

manual forspecific vehicleprocedures.


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AUDIO NETWORKS

Self-test procedure:

Codes are shown in the control panel display.


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AUDIO NETWORKS

This type of network must have both databus wires in tact.

If either wire fails, there will be a loss of

communication between modules.


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AUDIO NETWORKS

The entire network will be disabled if eitherwire is:

Shorted to power

Shorted to ground

Shorted to each other


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AUDIO NETWORKS

If a wire opens, any module after the openwill not operate.

The rest of the system will operate normally.


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CAN (CONTROLLER AREA NETWORK)

Low cost network that allows high-speedmodule-to-module communication.

All manufacturers are required to use a CAN

network by 2006.


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Operates at up to 500 kilobytes per second.


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Communicatesover a twistedpair of wires.

CAN H (High)CAN L (Low)

The CANnetwork is

connected to theDLC on someapplications.


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NETWORK DIAGNOSIS

A scan tool may be used to test the network.

If the module is unable to communicate withthe scan tool, the scan tool will identify that

there is a network problem.


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NETWORK DIAGNOSIS

Reasons for no communication Insufficient power

Insufficient ground

Network circuit failure

Module failure


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NETWORK DIAGNOSIS

Communication may fail due to the vehiclenot being equipped with the module.


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SCAN TOOL DIAGNOSIS

Scan tools may be used to:Perform on-demand self tests

Retrieve Diagnostic Trouble Codes (DTCs)

Monitor and record live data

Control outputs


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SCAN TOOL DIAGNOSIS

U-code identifies that the:Module did not receive the data it expected.

Data is invalid or missing.


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SCAN TOOL DIAGNOSIS

A U-code may be due to an input failure.


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SCAN TOOL DIAGNOSIS

A U-code may be due to a network failure.


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SCAN TOOL DIAGNOSIS

Live Data can be viewed from severalmodules at the same time.


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SCAN TOOL DIAGNOSIS

A scan tool can send a request to a moduleto command an output device.


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NETWORK DIAGNOSIS

A communication line can also be testedusing a DVOM by:

Testing for continuity between two modules.

Testing for voltage while communication is takingplace.

Always consult wiring diagrams for specific

vehicle information.Unplug/Reconnect Modules!(Scan Tool)


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SUMMARY

In this presentation, you learned:What an automotive computer network is and

how it works.

The differences between different types ofautomotive computer networks.

How to test an automotive computer network.

automotive computer networks

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