Electronic and computer controlled systems  course 673 technician handbook

Simple ECU InputsCombination Switch Voltage ON/OFF Oxygen Sensor Variable Voltage Voltage Pulse Pattern Active Speed Sensor MRE A MRE B Sensor IC Variable Resistance– In other types o

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Revision Date: June 22, 2009

TOYOTA Technical Training

Electronic & Computer Controlled Systems Course 673 Technician Handbook

Tai ngay!!! Ban co the xoa dong chu nay!!!

Technical Training i

Objectives Final Student Performances a

Section 1:

Diagnostic

Techniques and

Tools

Course Menu 3

Section 1 Topics 5

Electronic Control Units 6

How ECUs Work 7

Logic Function 7

Simple ECU Inputs 8

Voltage ON/OFF (Switch) Input 9

Variable Voltage Input 10

Variable Resistance Input 11

Pulse Pattern Input 12

Simple ECU Outputs 13

Transistors as Switches 13

Pulse Width Modulation 14

Duty Cycle 15

Power-Side Control 16

Self Diagnosis 17

Differences in Self-Diagnosis 17

ECU Memory 19

Types of ECU Memory 19

Customization 20

Initialization 21

Why Initialize? 21

Section 2: Overview of Multiplex Communication Section 2 Topics 23

Why Use Multiplexing 24

Applications of Multiplexing 24

Benefits of Multiplexing 24

Multiplexing 25

ECU Communication 26

Signaling Between ECUs 27

Communication Protocols 28

Multiplex Topology 29

Ring Topology 30

Two Opens in a Ring Network 31

Open in a Star Network 32

Open in a Bus Network 33

Single Wire vs Twisted-Pair 34

Advantage of Twisted-Pair Wiring 35

Section 3: Signals & Waveforms Section 3 Topics 37

Electronic Communication 38

Types of Waveforms 38

Waveform Measurements 39

Amplitude 39

Frequency 40

Pulse Width 41

Duty Cycle 42

Section 4: Measuring Signals Section 4 Topics 43

The Oscilloscope 44

PC Oscilloscopes 45

Basic Operation 46

Oscilloscope Scales 47

Repair Manual Suggested Scales 48

Repeating vs Changing Patterns 49

Capturing Waveforms 50

Scope Pattern Comparison 51

The Effect of Scale 52

Trigger Function 53

Other Trigger Uses 54

Advanced DVOM Features 55

MIN/MAX Recording 55

Peak MIN/MAX 55

Relative Delta 55

Frequency Measurement 56

Duty Cycle 56

Worksheet: DVOM Set-up & Advance Features 57

Instructor Demo: Using DVOM Resistance Setting 58

Section 5: Using a PicoScope™ Section 5 Topics 59 Introduction to PicoScope™ 60

Connecting the Leads 60

PicoScope Features 61

Auto Voltage Scale 61

Auto Setup 61

Manual Voltage Scale Settings 62

Manual Time Scale Settings 62

Turning the Trigger On 63

Setting the Trigger 64

Start and Stop Capturing 65

Technical Training iii

Section 6: Using

an Inductive

Clamp

Section 6 Topics 75

The Inductive Clamp 76

Polarity 76

Current Rating 77

Preparation for Use 78

Converting Measurements to Amps 79

Amp Clamp Applications 80

Diagnosing Short Circuits and Parasitic Draw 80

Diagnosing Motor Faults with an Oscilloscope 81

Worksheet: Inductive Current Clamp I: Measurement & Conversion 82 Worksheet: Inductive Current Clamp II: A/C Blower Motor 82

Section 7: Multiplex Circuit Diagnosis Section 7 Topics 83

Additional Properties of MPX Protocols 84

Communication Direction 85

Transmission Timing 86

Collision Detection 87

Data Casting 88

Sleep Mode 89

Wakeup Function 89

Body Electronics Area Network 90

Local Interconnect Network 91

LIN Characteristics 91

LIN Replacing BEAN 91

LIN Gateway Function 92

Controller Area Network 93

Terminating Resistors 93

Audio Visual Communication-Local Area Network 94

AVC-LAN Protocol 95

Gateway ECU 96

CAN Gateway ECU 96

Summary of Gateway ECU Functions 97

CAN Gateway ECU Functions 98

Transmit/Receive Charts 99

BEAN Signal 100

BEAN Diagnosis 101

Open Circuit 102

Short Circuit 103

Short Circuit Step 1 104

Short Circuit Step 2 105

Short Circuit Step 3 106

Short Circuit Step 4 107

Short Circuit Step 5 108

Short Circuit Step 6 109

Diagnosing a Large Network 110

Diagnosing with Techstream 111

Diagnosing a BEAN Open Circuit with an Oscilloscope 112

Worksheet: BEAN Network Diagnosis 113

Instructor Demo: BEAN Operation and Diagnosis 113

LIN Signal 114

LIN Diagnosis 115

Worksheet: A/C LIN Interface 116

CAN Signal 117

CAN Diagnosis 118

Short Between CANH and CANL 118

Short to B+ or Ground 118

Opens 119

CAN Bus Check 120

Location of DLC3 120

Terminating Resistors 121

Resistance Tests on CAN Circuits 122

Worksheet: CAN Diagnosis 124

Instructor Demo: CAN Resistance Test Precautions 124

Worksheet: CAN Main Bus Faults 125

Worksheet: CAN Sub Bus Diagnosis 125

AVC-LAN Signal 126

AVC-LAN Diagnosis 127

AVC-LAN DTCs 128

Worksheet: AVC-LAN Inspection 129

Other Multiplex Circuits 130

A/C Servo Motor Circuits 130

BUS Connectors 131

Pulse-Type Servo Motors 132

Worksheet: A/C Bus Servo Motor Operation & Diagnosis 133

Section 8: Electronic Systems Section 8 Topics 135

Engine Immobilizer Function 136

Engine Immobilizer Operation 137

Key Code Registration 137

Master Keys and Sub Keys 138

Automatic Key Code Registration 139

Watch for Error Codes 139

Ending Automatic Registration 139

Configuration in Earlier Models 140

Technical Training v

Transponder Key Amplifier Terminal Values 150

ECM Terminal Values 151

Worksheet: Immobilizer 152

Power Distributor 153

Protect Mode 153

Mode Monitor Terminal 153

Smart Junction Box (MICON) 154

High Intensity Discharge (HID) Headlights 155

Dynamic Laser Cruise Control Operation 156

Laser Sensor 157

Indicators 158

Error/Cancellation Codes 158

Constant Speed Control 159

Decelerator Control 160

Follow-Up Control 161

Accelerator Control 162

System Diagram 163

Distance Control ECU Waveforms 164

Laser Radar Sensor Waveforms 165

Appendix Appendix 167

Transistors 168

Transistor Types 169

How a Transistor Works 170

Transistor Switches 171

Transistor Amplifiers 172

Digital Circuits 173

Analog-to-Digital Converter 174

Logic Gates 175

Normal CAN Signal 176

CAN Shorts and Opens 177

Short CANH to CANL 177

Short CANH to B+ 178

Short CANL to B+ 178

Short CANH to Ground 179

Short CANL to Ground 179

Open in CANH or CANL (Main Bus) 180

Open in CANH and CANL (Main Bus) 181

BEAN Signals 182

BEAN Short to Ground 183

Normal BEAN, Dual Trace 184

BEAN Open Circuit, Dual Trace 185

Worksheets

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Technical Training a

Course 673 Electronic & Computer Controlled Systems

Final Student Performances Terminal Objective (Terminal FSP)

Given all of the applicable tools, equipment, and appropriate vehicles, the technician will be

able to apply a number of diagnostic techniques to monitor and repair faults in advanced

computer and electronic circuits

Technician Objectives (FSPs)

The technician will be able to:

1 Research information related to:

• The purpose and function of ECU terminals

• Inputs & Outputs

• Terminals of the ECU

• Power & Ground points

2 Identify inputs and outputs and determine how they affect ECU operation

3 Differentiate between:

• Pulse width & duty cycle

• Frequency & duty cycle

4 Identify the consequences of the following to the diagnostic process:

• Initialization (Memory Loss)

• Customization (CBEST)

• Sleep mode vs normal operation

5 Demonstrate proficient use of the advanced DVOM features

• MIN/MAX function

• Peak MIN/MAX function

• Measure frequency

• Measure duty cycle

6 Apply advanced DVOM functions for quick diagnostic evaluations

7 Practice using an Inductive Current Clamp with a DVOM to provide the ability to take

current readings without breaking into a circuit

8 Utilize an inductive Current Clamp to evaluate system operation & determine

diagnostic strategy

9 Practice conversion of voltage and amperage values to apply to inductive clamps that use

conversion factors for sensitivity

10 Monitor AC blower motor current using a DVOM equipped with an inductive current

clamp, and monitor current using an oscilloscope and inductive clamp

11 Properly set-up an oscilloscope

• Auto features

• Voltage & Time Scale Settings

• Horizontal & vertical rulers

• Trigger point

• Horizontal & vertical zoom features

12 Apply the basic features of the oscilloscope used in combination with the

Techstream Unit

13 Locate and back probe a dimmer-controlled interior lamp or LED, practice measuring

Voltage (V), Hertz (Hz), and percentage values (%) using a DVOM, and use an

oscilloscope to display the signal pattern

14 Set oscilloscope voltage and time settings appropriate to the circuit measured

15 Utilize oscilloscope patterns derived from a known good vehicle to verify normal

system operation

16 Differentiate between different oscilloscope patterns

17 Use an oscilloscope to confirm proper operation vs a faulty circuit

• Duty cycle

• Frequency

• Amplitude

18 Use an oscilloscope to identify intermittent faults

19 Capture, record, save and send oscilloscope waveforms

20 Identify Body Electronics Area Network topology and network operation

21 Perform fault diagnostics on a BEAN network

22 Identify Local Area Network topology and network operation

23 Monitor and diagnose the AC Control Assembly operation and LIN communication using

Techstream, an oscilloscope and TIS

24 Identify Controller Area Network topology and network operation

25 Use an ohmmeter and an oscilloscope to observe CAN High and CAN Low; diagnose a

short to ground and an open circuit on CAN High and CAN Low; and short CAN High to

CAN Low to observe the results

26 Develop a strategy to diagnose a CAN Network fault using the EWD, a Techstream CAN

Bus Check, and the information provided

27 Identify Audio Visual Communication-Local Area Network topology and network operation

28 Create, monitor and diagnose an AVC-LAN System amplifier malfunction using

Techstream and an oscilloscope

673 Electronic & Computer Controlled Systems

Welcome Toyota Technicians

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Course Menu

• Electronic Control Units

• Overview of Multiplex Communication

• Signals & Waveforms

• Measuring Signals

• Using a PicoScope™

• Using an Inductive Clamp

• Multiplex Circuit Diagnosis

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Technical Training 5

• Electronic Control Units

• Logic Function

• Simple ECU Inputs

• Simple ECU Outputs

Electronic Control Units

Electronic Control Units

In the 1970’s, the decreasing cost and increasing power of computerized

microprocessorslaunched the personal computer industry Because of their speed and flexibility in carrying out complex functions, microprocessors were adapted for hundreds of uses beyond personal computers

The first microprocessors began appearing in automotive engine control systems in the early 1980s In automotive applications, they became known

as electronic control units (ECUs) Today, some vehicles may have

dozens of ECUs controlling a wide variety of vehicle systems, including:

Technical Training 7

ECU Logic Function

ECUs have electronic logic circuits that “make decisions”

by evaluating conditions according to predetermined rules.

Light Control SWLight Control Sensor

Headlights

TaillightsBody ECU

An ECU is a small computer programmed to perform a specialized function in the vehicle As with any computer, it operates on the principle of input, processing, and output

Input –Information about conditions is supplied to the ECU as input signals Input can be provided by:

For an example of the ECU’s logic function, consider the lighting control system which is within the Body ECU A simple lighting control system uses three inputs – the light control switch, the light control sensor, and the ignition switch

When the condition of these three inputs matches the conditions preprogrammed in the ECU, the ECU turns on the headlights and taillights

Logic Function

How ECUs

Work

Simple ECU Inputs

Combination Switch

Voltage ON/OFF

Oxygen Sensor

Variable Voltage

Voltage Pulse Pattern

Active Speed Sensor

MRE A MRE B Sensor IC

Variable Resistance– In other types of sensors, electrical resistance increases or decreases as external conditions change Sensing the changing voltage as a result of changing resistance in the circuit signals the ECU what the conditions are

Variable Pulse Pattern– Another method for signaling the ECU about changing conditions is to turn a circuit on and off rapidly at a particular frequency This works especially well for signaling rotational speed It is the frequency of the ON/OFF pulses that supplies information to the ECU

Simple ECU

Inputs

ON: V = 0.1V

(available voltage)

Voltage can also be measured

at the ECU terminal

The ECU detects the state of a ground-side switch by reading the

The diagrams above illustrate a ground-side switch connected to an ECU

The ECU supplies battery voltage to the switch circuit and provides the circuit’s load (a resistor) The ECU’s electronic circuits detect when the voltage after the load is high (near battery voltage) or low (near ground voltage)

While the switch is open, no current is flowing and the available voltage after the load is near battery voltage When the switch is closed, current flows and most of the battery voltage is dropped across the load The available voltage after the load is now near ground voltage

In this example, the switch controls a lamp, but is not actually part of the lamp circuit When the ECU senses a voltage drop in the switch circuit, it supplies five volts to the transistor This in turn closes the lamp circuit, lighting the lamp

You can detect the same high or low voltage the ECU is detecting by measuring voltage at the appropriate ECU terminal If the switch is closed and the voltage remains high, you’ll know there is an open in the circuit between the ECU and the switch

The actual wiring inside the ECU is extremely complex The ECU circuit details shown in the diagrams above and the diagrams on the following pages are to illustrate concepts, not actual internal connections.

Voltage ON/OFF

(Switch) Input

NOTE SERVICE TIP

Variable Voltage Input

The oxygen sensor is a voltage generator.

V> 0.45v : air-fuel ratio too rich

V= 0.45v : air-fuel ratio correct

V< 0.45v : air-fuel ratio too lean

Atmosphere

Voltage

The engine control module

interprets the voltage to make

corrections to the air-fuel ratio

V

Exhaust Gas

An oxygen sensor is a voltage generator, producing between 0.1v and 0.9v

depending on the oxygen content of the exhaust gas compared to the atmosphere

The engine control module’s electronic circuits measure the amount of voltage generated by the oxygen sensor, and use that information to control the air-fuel ratio

Variable Voltage

Input

Technical Training 11

Variable Resistance Input

A temperature sensor is a type of variable resistor.

Its resistance changes with temperature

12.6V or 5V

An ECU can detect the change

in the sensor’s resistance by measuring voltage

ECU

V

A temperature sensor is a type of variable resistor whose resistance changes with temperature This type of sensor is often called a thermistor

Two types of thermistor are:

Positive temperature coefficient (PTC) thermistor– resistance increases

Variable Resistance Input

Pulse Pattern Input

An active wheel speed sensor generates a series of voltage pulses

as the wheel rotates

As rotation speed increases, pulses are generated at a higher frequency

Lower Rotation Speed

Voltage

Time

Voltage

Time

Higher Rotation Speed

The ECU measures the pulse frequency

to calculate vehicle speed

MRE A MRE B Sensor IC

Another type of ECU input is a pulse pattern When voltage rises

momentarily, then falls, the transient voltage reading is called a pulse When

a component creates multiple pulses, the result is a pulse pattern (or pulse

train)

An active wheel speed sensor is a component that generates a pulse pattern

A magnetic ring mounted on the wheel hub has alternating north-south fields that are detected by the sensor pickup As the wheel rotates, the alternating magnetic fields are converted into a series of voltage pulses The frequency

of the pulses increases with the wheel rotation speed

When the pulse pattern is provided as ECU input, the ECU’s circuits are able

to measure the pulse frequency and calculate wheel RPM and vehicle

speed

Pulse Pattern

Input

Technical Training 13

See Appendix for More Info

A

Simple ECU Outputs

When the operating conditions are met, the ECU makes a

connection to power or ground to energize a circuit

B+

ECU

Transistor

Ground-side controlled circuit

Power-side controlled circuit

Collector

BaseEmitter

How a Transistor Works (NPN)

When voltage

is applied to the base…

current can flow from the collector to the emitter

The simplest way for an ECU to control a vehicle function is to turn a circuit

on or off A circuit can be ground-side switched or power-side switched

Electronic circuits use transistors for switching circuits on and off A

transistor is a solid-state electronic component having a base, collector and emitter In the more commonly used NPN transistor, when sufficient voltage

is applied to the base, current flows from the collector to the emitter

One of the advantages of the transistor is that a low voltage at the base is able to control a large current flowing through the collector and emitter In that respect, a transistor is similar to a relay

Some transistors also regulate current flow based on the amount of voltage applied to the base Within the transistor’s limits, a higher base voltage results in a greater flow of current through the collector/emitter This feature

is used in amplifier circuits where the low voltage signal from a microphone regulates current flow in higher power speaker circuits

Simple ECU

Outputs

Transistors as

Switches

Pulse Width Modulation

The ECU can open and close a circuit rapidly to control

component operation

The process of varying the amount of time a circuit is ON is called pulse width

modulation

The ECM regulates the injector

ON time by regulating the width of the voltage pulse to the injectors

Notice the pulse width increases at higher load as the ECM increases the injector ON time

Voltage Pulses

Example

Pulse Width

An ECU’s electronic circuits have the ability to open and close a circuit very rapidly The ECU can switch a circuit on for a fraction of a second at very precise intervals

When a circuit is switched ON and then OFF, the momentary change in voltage

creates a voltage pulse (The pulse can be either a momentary increase or

decrease in voltage depending on whether the circuit is ground-side switched

or power-side switched and where the voltage is measured.)When the voltage is viewed on an oscilloscope, the voltage pulse’s width represents the amount of time the circuit is switched ON and can be as brief as

1 millisecond or less In some circuits, the ECU uses the amount of ON time to regulate component operation

When the ECU varies the width of the voltage pulse (the ON time) to control a

component, the process is called pulse-width modulation.

In the above example, the frequency of the pulses changes as well as the

Pulse Width

Modulation

NOTE

Measuring Duty Cycle

When the ECU modulates a circuit at a constant frequency, you can measure

the circuit’s duty cycle Duty cycle is the percentage of ON time compared to

total cycle time.

In a ground-side controlled circuit, measure after the load.

5V

1 cycle (100%)

25% ON (grounded)

1 cycle (100%)

The terms pulse-width modulation and duty cycle are often confused or

used incorrectly

Pulse-width modulationis a function an ECU can perform to turn a circuit on and off rapidly to regulate the amount of ON time As the pulse width changes, the frequency of the pulses might or might not change depending on the circuit design and intended operation

When a circuit is switched on and off rapidly at a constant frequency, duty

cyclemeasures the percentage of ON time compared to total cycle time If the circuit is ON 75% of the time, it is operating at a 75% duty cycle When a circuit

is duty-cycle controlled, the pulse frequency does not change – only the percentage of ON time

An ECU varies the duty cycle to control the speed of a motor or the brightness

of a lamp by switching the circuit ON and OFF hundreds of times per second Human senses can’t perceive a lamp or motor being cycled on and off that quickly Nonetheless, the amount of power to the component increases or decreases depending on how much of the time the circuit is ON versus OFF

As OFF time increases, the net power supplied to a component decreases resulting in the lamp becoming dimmer or the motor running slower As ON time increases, power increases and the lamp becomes brighter or the motor runs faster

When the circuit is ground-side controlled, voltage before the load is always battery voltage, and voltage after the switch is zero, or near zero To observe voltage modulation, place the positive probe between the load and the switch (which may be an ECU)

Duty Cycle

NOTE

Measuring Duty Cycle

Signals in a power-side controlled circuit are the opposite of

signals in a ground-side controlled circuit

75% ON (powered)

In a power-side controlled circuit, measure before the load.

B+

If the percentage of ON time decreases, the lamp becomes dimmer

25% ON (powered)

1 cycle (100%)

1 cycle (100%)

ECU

Most circuits in Toyota vehicles are ground-side controlled When a width modulated circuit is power-side controlled, the voltage modulation is observable after the ECU and before the load In this arrangement, the circuit is ON when the voltage rises

pulse-Note that if voltage is measured after the load, a very minute change in voltage occurs as the circuit is modulated At this point in the circuit, voltage is zero when the circuit is open When the circuit is closed, ground voltage is present The difference is usually less than 0.1V and may not be observable depending on your scope settings

Power-Side

Control

Technical Training 17

Self-Diagnosis

The ECU’s internal wiring can be arranged so it can detect

when an input circuit is open or shorted to ground.

Throttle Position Sensor

ECM

VTA

VTA2 VC

E2

Under normal conditions, the ECM senses more than 0V and less than 5V at VTA and VTA2

A significant reason ECUs have become so common in automobile systems

is their ability to perform self-diagnosis ECUs can identify faults in circuits,

components, and even within the ECU itself When a fault is detected, the ECU can:

• Illuminate a warning light

• Set a diagnostic trouble code

• Begin operating in a fail-safe mode by:

◦ Disabling a system that is working incorrectly

◦ Using sensor data from alternate sources

◦ Applying alternate rules for operating the vehicle or subsystem

to maintain maximum safety

An ECU’s self-diagnosis capabilities can range from very simple to highly sophisticated Each ECU has its own features and limitations, and very few work in exactly the same way

The example above is a throttle position sensor circuit The electronics inside the engine control module (ECM) are designed so that an open or a short to ground on VTA or VTA2 can be detected and a DTC set The circuit arrangement inside the ECM is not able to distinguish a short from an open, however In either case, the voltage the ECM is monitoring goes to 0V

Self-Diagnosis

Differences in

Self-Diagnosis

Throttle Position Sensor

ECM

VTA1

VTA2 VC

E2

5V

Self-Diagnosis

ECUs can be wired so they can detect the difference between

an open or short, and set a different DTC for each.

DTC P0122 Throttle/Pedal Position Sensor/Switch “A”

Circuit Low Input DTC P0123 Throttle/Pedal Position Sensor/Switch “B”

What is the normal voltage at VTA2?

In this arrangement, what is the normal voltage at VTA1?

What is the voltage with a short in the circuit?

What is the voltage with an open in the circuit?

In this throttle position sensor circuit, the electronics inside the ECM are arranged slightly differently In this arrangement, a short to ground on a VTA line causes the monitored voltage to go to 0V An open in a VTA line, however, causes the monitored voltage to go to 5V

Thus, this ECM can distinguish between an open or short on an input circuit and can set a DTC for one or the other The additional data supplied by the ECM makes it easier and faster to diagnose and correct the problem

Differences in

Self-Diagnosis (Cont’d)

Technical Training 19

Like other computers, ECUs have internal memory Besides storing DTCs, they can also store switch settings and component positions Over time, ECUs can acquire and store information about the vehicle’s operating characteristics and driver/occupant preferences The data stored in memory can have a direct affect on how well the vehicle operates and the driver’s perceptions of comfort and convenience

Volatile memorychips are the type that require constant power to maintain what is stored in them When the power is removed, their memory contents are erased These types of memory chips are used for ordinary

microprocessor memory (RAM for example.)

Non-volatile memorychips retain their contents even when the power is removed These types of memory chips permanently store the

microprocessor’s operating instructions, or logic (ROM for example.)

Programmable Read Only Memory (PROM)– A memory chip that can be programmed once, but cannot be reprogrammed

Erasable Programmable Read Only Memory (EPROM)– A programmable chip that can be removed from its circuit and reprogrammed

Electrically Erasable Programmable Read Only Memory (EEPROM)– A programmable chip that can be electrically erased and reprogrammed without removing it from the circuit

ECU Memory

• DTCs

• Driver preferences

• Vehicle operating characteristics

ECUs have different types of memory.

RAM (volatile) ROM (permanent) EEPROM (reprogrammable)

ECU program logic

ECU program logic, data

(reflash)

Types of ECU

Memory

ECU Memory

ECU Customization

Because ECUs have memory, they can be programmed with

owner/driver preferences.

Main Body ECU

Would you like the interior light turned ON when the doors are unlocked?

Would you like the interior light turned ON when the ignition is turned OFF?

How long would you like the interior lights to

No matter how carefully automobile manufacturers analyze the features that new car buyers want, there will always be those who want a feature to work differently ECUs have made it much easier for owners to customize many of the vehicle’s convenience features to suit their own preferences

The settings for customizable features are stored in ECU memory Needless

to say, if the memory is lost then any preferences the owner has chosen are also lost Memory can be lost when the ECU loses its connection to the battery, and also when the ECU is replaced

Before disconnecting the battery, make note of the owner’s customized settings and restore those settings when service is complete

When one driver changes a customized setting without informing other drivers, another driver may view the change in operation as a malfunction Be sure to consider the potential role of customized settings on a customer’s concern before beginning a problem diagnosis

Customization

SERVICE TIP

NOTE

Technical Training 21

ECU Initialization

Initialization procedures can be very different depending on the ECU

• Unload the vehicle

• Jumper terminals 4 and 8 of DLC3

• Flash the headlights 3 times

Headlamp Leveling ECU Initialization

Driver’s Door Power Window Initialization (Body ECU)

• Turn ignition ON

• Hold the switch to open the window

• Hold the switch to close the window

• Keep holding the switch until the switch stops blinking

Examples

Completely Closed

ECUs may need to be initialized when:

• A new ECU is installed

• Key components related to the ECU’s operation have been replaced

• Loss of power erases critical memory settings

Initializing an ECUsimply means preparing it for operation If an ECU is not initialized when required:

• The system may be inoperable or operate incorrectly

• Some system features may be disabled

When an ECU is installed, it becomes part of a system of interconnected components Many ECUs are designed to work in systems with optional components in sometimes varying configurations

Before the ECU can begin operation, it must learn the configuration of the system it’s connected to, and sometimes obtain data from other components.This takes place during initialization When initialization is completed, the ECU has acquired the information it needs to begin performing its function

In quite a few vehicle systems, ECUs control motors, such as power window

motors and power back door motors These systems require initialization in particular so the ECU can synchronize itself with the motor to control the

opening and closing function properly In systems with jam protection, this

feature may be inoperable until the ECU has been initialized

Before determining an ECU is faulty, first verify that it doesn't just need to be initialized

Initialization

Why Initialize?

NOTE

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• Why Use Multiplexing?

• How ECUs Communicate

Why Use Multiplexing?

One multiplex circuit does the work of many conventional circuits.

• Fewer wires

• Lighter wiring harnesses

• Simpler, more reliable wiring

point-Control modules use the data received to control functions such as anti-lock braking, turn signals, power windows, dashboard displays, and audio systems

In-vehicle networking provides a number of benefits:

• Each function requires fewer dedicated wires, reducing the size of the

wiring harness This yields improvements in system cost, weight,reliability, serviceability, and installation cost

• Common sensor data, such as vehicle speed, engine temperature, etc

are available on the network, so data can be shared, thus eliminating

Benefits of

Multiplexing

Applications of

Multiplexing

What is Multiplexing (MPX)?

Multiplexing is a way to use one wire to communicate between many devices

Conventional wiring between components

MPX communication line

Light

Motor

Heater

Solenoid Switch

ECU ECU

In conventional electrical circuits, each voltage signal between components requires its own dedicated wire The presence, absence, or amount of voltage on the wire (supplied by a switch or a sensor, for example) controls the operation of a component on the other end

In a multiplex circuit, a computer chip on one end of a single wire can transmit a series of coded voltage signals that can be interpreted by a

computer chip on the other end The computer chips are inside electronic

control units (ECUs), and the coded voltage signals are data packets.

A data packet may instruct the receiving ECU to:

• Turn on a light

• Start a power window motor

• Activate a solenoidBecause the data packets are sent in series, multiplexing is also referred to

as serial communication or serial networking, and the communication line

is called a serial data bus.

Multiplexing

How ECUs Communicate

ECU Logic Circuit:

To communication line:

• Supply voltage when transistor is OFF

• Ground voltage when transistor is ON

• Controls the ON/OFF signal

• “Reads” the data on the MPX line

• Performs self diagnosisECU

When the transistor is OFF, no current flows Referring to the diagram above,

if you were to measure the available voltage on the communication line, you would find supplied voltage

When the transistor is turned ON, current flows and all of the available voltage is dropped across the resistor Now the voltage measurement on the communication line (after the resistor) is ground voltage

By turning the transistor ON and OFF in a timed sequence, the ECU can

send a message to another ECU, similar to sending a message in Morse

code Part of the message, called a data packet, indicates which ECU the

message is addressed to Other ECUs listening to these messages ignore the ones not intended for them

The ECU communication line is powered through a resistor that acts as a load in the circuit This is commonly called a pull-up resistor If the circuit is

ECU Communication

NOTE

Signaling Between ECUs

Sender Supplies B+

Receiver Supplies B+

Sends signal

ECU ECU

12V

ECU ECU

When one ECU signals another, the one sending the signal is

not necessarily the one supplying the power to the circuit

Sends signal

12V

In diagnosing ECU controlled circuits, don’t make the assumption that the ECU sending a signal is the one supplying the circuit voltage As shown in the illustrations above, it’s possible for the ECU receiving a signal to be the one providing power to the circuit

Signaling

Between ECUs

Protocol BEAN

(TOYOTA Original)

CAN (ISO Standard)

LIN (Consortium)

AVC-LAN (TOYOTA Original) Application Body Electrical Power Train Body Electrical Audio Communication

500 kbps (HS)*

Communication Wire

AV Single Wire Twisted-pair wire AV Single Wire Twisted-pair wire

Drive Type Single Wire

Voltage Drive

Differential Voltage Drive

Single Wire Voltage Drive

Differential Voltage Drive Voltage 10+ volts 2.5v to 3.5v CANH

2.5v to 1.5v CANL 8 volts

2v to 3v TX+

2v to 3v

Communication Protocols

A “protocol” is the set of rules and standards for communication

between components.

BEAN:Body Electronics Area Network

CAN:Controller Area Network

LIN:Local Interconnect Network

AVC-LAN:Audio Visual Communication - Local Area Network

* Up to 1 Mbps

The rules and standards for transmitting and receiving data packets between

ECUs are called a protocol Some protocols provide faster exchange of

messages between components and more reliable operation than others As speed and reliability increases, so does the cost

The chart above compares some of the characteristics of the different protocols found in Toyota vehicles

• BEAN is the earliest protocol used by Toyota Based on early technology,

it is also one of the slowest protocols BEAN is typically used for body electrical systems such as lights, locks, windows, and air conditioning

• AVC-LAN is another early protocol developed by Toyota as a faster

alternative to BEAN for audio, video, and navigation components

• CAN, the ISO standard for automotive applications, is a high-speed

protocol for critical vehicle systems such as engine control, braking, collision, and SRS systems

pre-• LIN is an alternate, low-speed standard protocol developed in later years Communication

Protocols

Multiplex Topology

Star Style Each ECU is connected directly to a master

ECU with a central control function

Bus Style

All ECUs are connected to a single common communication line

Daisy Chain Style

The ECUs are connected in a combination

ring and bus form

Applies to CAN

Applies to LIN and AVC-LAN

Applies to BEAN

ECU ECU

ECU

ECU

ECU

ECU ECU

ECU ECU

Master ECU

• Bus In the bus style, multiple ECUs are connected to a single common

communication line, allowing each ECU to transmit or receive signals directly with any other ECU on the network

• Ring ECUs connected in a ring have two network lines to provide a

backup path for communication If one communication line is disconnected, the ECU can still receive network communications on the other line

• Star The star style uses a central ECU called a master to control the other ECUs in the network (slaves) In this configuration, slaves cannot

communicate directly with one another without passing the message through the master

• Daisy Chain Sometimes a multiplex circuit can combine two design

types An example is a BEAN circuit with both ring and bus topologies

Components on a network are referred to as nodes ECUs are not the only

possible nodes Sensors with multiplex communication capability can also be

nodes on a network Examples are steering angle sensors and yaw rate

Ring Topology

In a ring network, a single open circuit in the loop does not affect

performance.

Communication lines (bus)

One open wire does not affect network operation

When network components are connected in a ring, every component has

two paths for sending messages to another component The advantage of ring topology is added reliability because the network continues to operate normally in the event of an open wire anywhere in the multiplex circuit

Ring Topology