Audi 90 1993 Service Manual/electrical Wiring Diagrams

Service

Electrical

Wiring Diagrams

USA/Canada

m.y.

1993 ·

Technical Service Communications

This publication contains electrical wiring diagrams for the Audi 90, model

year 1993, sold in the USA and Canada. Whenever working on Audi vehicles, follow the procedures described on the appropriate Repair Manual Microfiche. Use of tools or procedures other than those recommended may be

detrimental

the safe operation of the vehicle as

well as the safety of the person doing the repair.

Before working on any car, read Warnings and Cautions.

Technical Service Communications

latest product information available at the time of printing. The right is reserved to make changes at any time without notice. No part of this publication may be reproduced, stored in a retrieval system, transmitted in any form or by any means, electronic, mechanical, photocopying, recording permission of the publisher. This includes text, figures and tables.

©Audi

Printed 9/94

W42 WD

America, Inc.

BOOK

this manual is based

otherwise, without the prior written

General

Cautions and warnings .......................................... · ... i

How to read wiring diagrams ..................................

Standard circuit/terminal designations .................. vi

Standard wire/connector designations .................. vii

Symbols used in wiring diagrams ..........................•

Test equipment ...•.............................................. ~ ...

Troubleshooting procedure ................•................

Wiring harness repairs .................................

iii

viii

•.

....•... xv

{Up

90-AII Models

VIN: 8 CPA 000100)

USA/Canada

ABS combi relay (2-wheel drive system) .............

ABS Control Module (2-wheel drive system) ......

ABS Quattro (with rear differential lock) ..............

Airbag triggering unit .............................................

AM/FM

Ashtray lights .........................................................

Auto check system ................................................

Automatic climate control ................................

Automatic transmission and cruise control

Auxiliary/relay panel, rear ....................

Auxiliary relay panel with connector station .......... 6

Back-up

Brake light switch ..................................................

Central locking system .......................................... 45

Cigarette Connections and Connector identification Cruise

Daytime running

Digital clock ............................................................ 27

Dual horns .............................................................. 39

ECM (Engine Control Module) .............................. 19

8-Way power front driver's seat

Emergency flasher relay ....................................... 37

Emergency switch .............................

Engine compartment light .....................................

Engine oil pressure sensor ................................... 57

Engine

stereo radio (anti-theft) with 6-speakers.

(2-wheel

drive) ..................................................... 85

light switch .............................................. 40

lighters ..........................

plugs on fuse/relay panel, rear . 9

control, Control Module ................

lights (Canada only) ................. 97

oil temperature sensor ............................. 57

.......

........

connector station ....... 8

/o memory) ...

...

.................

....

............... 7

...

41 63 55 69

....

...

....

... 48

.......... 44

60 37

Fuse

panel

........

...............

Fuse/relay panel ...................................................... 1

Generator (GEN) ...........

Glove compartment light Heated door

Heated front seats .............................................

Ignition/starter switch ............................................

Instrument cluster ........

Interior lights .......................................................... 50

Lamp Control Module, front .................................. 32

Lamp Main wiring diagram index

Manual

Mini-check system ...........................................

Mirror adjustment switch ............

locks ............................................

Control Module, rear ................................... 33

air conditioning ....................................... 1

......................................

...................................... 17

.....

.................................. 35

... 1 05

....

...................................... 29

.................................. 1 0

...

......................... 54

1 07

. 118

Index

Power window Control Module .............................

Power windows ...................................................... 53

90-AII Models

(Up to VIN: 8

USA/Canada

(Continued)

CPA

000100)

Reading

Seat belt

Servotronic Control Module .................................. 56

Starter Tilt and slide power sunroof ..

Windshield wiper intermittent switch .............

ABS Control Module ............................................ 157

ABS Quattro ......

Airbag

AM/FM stereo radio with 6-speakers .......

Auto check system .............................................. 142

Automatic

(Automatic transmission) ......

Automatic

(Manual

Automatic transmission ................

Auxiliary/relay panel, rear .................................

Auxiliary relay panel with connector station ...... 132

Battery .

Central locking system ........................................

Cruise control, Control Module ........................... 158

lights ........................................................ 50

warning Control Module ........................ 36

....

................................................................. 17

...

.......................... 128

.......

....

.................................

Control Module ......................................

climate control

..........................

climate control

transmission) ....................................

....

..................................

...

........... 165

...

.......

.. ..

..................... 189

...

...................... 134

153 171

176 183 132

151

90-AII Models

(From VIN: 8

USA/Canada

CPA

000100)

Daytime running ECM

(Engi 8-Way power front driver's seat (w/o Engine compartment Emergency Emergency Engine

Engine oil temperature sensor ........................... 160

Fog lights .............................................................. 149

Fuel pump ..........................................................

Fuse/relay panel .........................

Generator ..........

Glove compartment light ...................................

Ground connectors .............

Heated door Heated front seats

Ignition/starter switch ............

Instrument cluster Interior lights

Lamp Control Module, front .

Lamp

Light switch .......................................................... 145

oil pressure sensor ................................. 160

Control Module, rear ................................. 143

lights (Canada only) ............... 195

Control Module) ......

light ................................... 146

flasher relay ....................

flasher switch ............................

....

.............................

locks ............................................... 202

....

........................................... 205

....

.......................................

........................................................ 150

...................... 135

memory).

................. 147

....

...

....

.....................

...

............... 134

............................... 133

...

...................

....

........................... 144

........

...

162

147

138 131

146

139 140

Index

Manual air conditioning

(Manual transmiss ion) .

Mini-check system ............................................... 215

Mirror adjustment switch ..................................... 154

...

.................................. 210

90-AII Models

(From VIN: 8 CPA 000100)

USA/Canada

(Continued)

Power sunroof ............................................

Power windows .................................................... 156

Power windows

Radio

Reading lights ......................................................

Servotronic Control Module ................................

Starter ...................................................................

Windshield wiper intermittent switch .................. 148

..............................................

Control Module ....................

....

...

......

........ 220

...

.. 155

...

....

159 150

157 134

Index

Please read these WARNINGS and CAUTIONS before proceeding with maintenance and repair work.

• If you lack the skills, tools and equipment, or a suitable workshop for any procedure described this manual, we suggest you leave such repairs to an authorized Audi dealer or other qualified shop. We especially urge you to consult an authorized Audi dealer before beginning repairs still be covered wholly or in part by any of the extensive warranties issued by Audi.

• Audi is constantly improving its cars and sometimes these changes, both in parts and specifications, are made fore, part numbers listed in this manual are for

reference only. Always check with your authorized

dealer parts department for the latest informa-

Audi tion.

• Never work under a lifted car unless it is solidly supported on stands designed for this purpose. Do not support a car on cinder blocks, hollow tiles or other props that may load. Never work under a car that is supported solely by a jack. Never work under the car while the engine is running.

• If you are going to work under a car make sure that the ground is level. Block the wheels

to keep the car from Ground (GND) strap to prevent others from starting the car

• Never run the engine unless the work area is well

ventilated.

• Tie long hair behind your head .

necktie, a scarf, you work near machine tools or running engines. If your hair, clothing, or jewelry were the machinery, severe injury could result.

• Illuminate the work area adequately but safely. Use a portable safety light for working inside or under the car. Make sure the wire cage . The hot filament of an accidentally broken

• cannot cause electrical shorts, get caught in running

machinery, or be crushed by heavy parts.

while you are under it.

bulb can ignite spilled fuel or oil.

Finger rings should be removed so that they

applicable to earlier models. There-

crumble under continuous

rolling. Disconnect the battery

Carbon monoxide kills.

loose clothing , or a necklace when

any car that may

the ground,

not wear a

get caught in

bulb is enclosed by a

• Disconnect the battery Ground on

ever you work system. Do not smoke or work near heaters or other fire hazards. Keep an approved fi handy.

• Any time the battery has been disconnected it will

be necessary to reestablish Basic Settings for the Engine Control Module (ECM) and, on automatic transmissions, the Transmission Control Module (TCM), using the VAG

• On sure you know the correct radio activation code before disconnecting the battery or removing the radio. when power is restored, that radio may lock up and be rendered then entered.

• Do not attempt not yourself and others if you are tired, upset or have taken medicine or any other substance that may impair you from being

• Always observe good workshop practices. Wear goggles when you operate machine tools or work with battery acid. Gloves or other protective clothing should be worn whenever the job requires working with

• Do not re-use any fasteners that are worn or deformed in normal use. Many fasteners are designed to be used only once and become unreliable and may fail when used a second time. This includes, self-locking nuts or bolts, circlips, cotter pins. Always follow recommendations given tion. Always replace these fasteners with new parts.

• Friction materials such as brake pads and clutch discs may contain asbestos fibers. Do not create dust by grinding, sanding, or by cleaning with compressed air. Avoid breathing asbestos fibers and asbestos dust. Breathing asbestos can cause serious diseases such as asbestosis or cancer, and may result

cars equipped with anti-theft radios, make

If the wrong code is entered into the radio

feel well. You increase the danger of injury to

harmful substances.

but is not limited to, nuts, bolts, washers,

death.

the fuel system or the electrical

inoperable, even if the correct code is

work

fully alert.

NO)

strap when-

extinguisher

vehicles with

1551

Scan Tool (ST).

your vehicle

this publica-

you do

I General Information I Warnings/Cautions

Please read these WARNINGS and CAUTIONS before

proceeding with maintenance and repair work.

• Catch draining fuel, oil or brake fluid containers. Do not use empty food or beverage containers that might mislead someone into drinking from them. Store flammable fluids away from fire hazards. Wipe up spills at once, but do not store the oily rags, which can ignite and burn spontaneously .

Keep sparks, lighted matches, and open flame

• away from the top of the battery. If escaping hydro-

gen gas is ignited, it

and cause the battery to explode.

The air-conditioning (A/C) system is filled with a

• chemical refrigerant that is hazardous. The AIC system should be serviced only by trained technicians using approved refrigerant equipment, tra ined in related safety precautions, and familiar with regulations governing the discharging and disposal of automotive chemical refrigerants.

• Do not expose any part of the A/C system to high temperatures such as open will increase system pressure and may cause the system to burst.

• Some

equipped with a that a frontal impact. The airbag is operated by explosive device. Hand led improperly or without adequate safeguards, it can be and cause serious personal injury . To guard against personal injury or airbag system failure, only trained Audi Service technicians or service the airbag system.

• Never use a test light to conduct electrical tests

on the airbag system. The system must tested by trained Audi Service technicians using the Audi VAG equivalent. The airbag unit must never be electrically tested while

the vehicles covered by this manual are

automatically deploys

1551

will ignite gas trapped in the cells

recovery/recycling

flame. Excessive heat

supplemental restraint system (SRS),

airbag in the event of

accidently activated

should test, disassemble

Scan Tool (ST) or

is not installed in the vehicle.

approved

suitable

only be

• Before starting a job, make certain that you have all the necessary tools and parts the instructions thoroughly, do not attempt shortcuts. Use replacement Makeshift tools, parts and procedures will not make good repairs.

• Use pneumatic and electric tools only to loosen

threaded parts and fasteners, especially on light alloy fasteners

•

Be mindful of the environment and eco logy. Before you drain the crankcase, find out the proper way to dispose of the down a drain, or into a stream, pond or local

• Before doing any electrical welding on vehicles equipped with ABS, disconnect the battery Ground

(GND) strap and the ABS

• When boost charging the battery, first remove the fuses for the Engine mission Control Module (TCM), ABS Contro l Module, and the On-Board computer. In cases where one or more of these components is not fused, disconnect the Control Module connector(s).

•

ing) for longer than one minute, and do not exceed

16.5 attached. Wait at least one minute before boosting the battery a second time.

• Some aerosol tire inflators are highly flammable. Be extremely cautious when repairing a tire that may have been Keep sparks, open flame or other sources of ignition away from the tire repair area. tire at least four times before breaking the bead from the rim.

before attempting any repair.

tools appropriate to the work and use only

parts meeting Audi specifications.

parts. Always use a torque wrench to tighten

the tightening torque listed.

oil. Do not pour oil onto the ground,

ordinances that govern the disposal of wastes.

Control Module connector.

Control Module (ECM), Trans-

not quick-charge the battery (for boost start-

Volts at the battery with the boost ing cables

inflated usi

Completely remove the tire from the rim

an aerosol tire inflator.

hand . Read all

lake. Consult

separately

Inflate and deflate the

rnings/Cautions I General Information I

Fuse/Relay panel internal circuits (see Standard

CircuiVferminal

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~lgnations)

Fuse/Relay panel

~-~--~~~~~~~~~------~k

Relay (mounted on main fuse/relay panel)

Relay location (Example:

position #2)

Welded connection

wiring harness (see Positive (+)connections in

each

Circuit Section)

Internal connections (not

actual wires)

Component~

designation Component symbol

(see Symbols Used in Wiring Diagrams)

Wire size

and color (see Wiring Color

Code and

Wire Size)

Current track number

------

--------2.5

lo,-------...,F-------_....,-------~------41~e---tl~--connection

206

E87La

COOLANT FAN

J!Sm5coo

---·-t:;~

1.....-0,_

____

T r

2.5 0.5

RIBL

Mi----.it<--1

FAN~

-+___.

sPEHAeLAv

R/G

208 209

Ground (GND) connection (see Ground (GND) Connections in

each Circuit Section)

D75a

1.0

BUR

2.5

RIG

0.5

BUR

L---+-----Fuse/Relay

3/7sa

n====::z::;;:;;;:::l:::::::::::::::zi=rJ·

L.!:z;&&:;:z:::::::SS::;&::::::::::;::ll

2.5

R/W

0.5

BRIG

fr-

COOLANT

AFTER-RUN RESISTOR

FAN

2.5

RIBL

212 213

Current track reference

(Example: wire continues

at current track #238)

m/~~n~:~e:age

Fuse designation (position #20 30 amp rating)

2.5

RIG

panel

2130

COOLANT

~b'J~~~~ODULE

5fT

6.0

terminal designation

FAN

----

Component ground (GND) (through housing mounted to ground [GND])

(Example:

conn_ector termlnal75a)

Relay location on auxiliary relay panel (Example: position #18)

Terminal

designation (Example: panel socket

terminal

Wire connector

(Example: connector T3a terminal #3)

Ground (GND) path (Example: from welded harness

216 to chassis ground

connection 32)

#31

component)

I General Information I How to read wiring diagrams iii

Fuse

Thermo-fuse

(Circuit Breaker

Warm-up regulator Auxiliary air valve

Battery

Starter

Generator (GEN)

S.j_

Solenoid valve

Motor

Wiper motor, 2-speed

Switch (Manually

Switch

(Thermally operated)

operated)

Ignition coil

Distributor (Mechanical)

Push button switch

(Manually operated)

Switch (Mechanically operated)

Distributor

(Electronic)

Spark plug and plug

Glow plug Heater element

Automatic choke

Engine Coolant Temperature switch (ECT)

connector

Switch (Pressure operated)

Multiple switch (Manually operated)

Variable resistor (Rheostat)

Resistor,

temperature dependent

Relay

Relay (Electronically controlled)

!97-24291

iv Symbols used

wiring diagrams I General Information I

Resistance

Diode

Cigarette lighter

117\

lfllllll

~~nono1

Zener diode

LED

Instrument

(Gauge)

Electronic Control Module

Analog clock

Digital clock

Multi-function indicator

Rear window defogger heat element

Horn

Push-on connector

Multi-point connector on component

Wiring junction

Wiring connection detachable '

Wiring connection fixed '

Internal connection in a component

Buzzer

Consumption indicator

Speed sensor

bulb

Light

Light bulb (dual-filament)

Interior light

Resistance wire

Control motor, headlight range adjustment

Crankshaft Posit i

sensor

Slip contact

(CKP)

197-24291

General

Information

I Symbols used in wir ing diagrams v

Standard Circuit/terminal Designations

Circu it Number

Circuit Description Most Common

15 Powered when ignition switch is Black (BK)

"On"

"Start" positions

"On" position

"Start" position)

battery

(-)

side of switching relay Brown (BR)

negative(-)

31 50

D+

Load-reduction circuit Powered by load-reduction relay when ignition switch in (Not powered

Battery positive(+) Voltage Red (R) Powered whenever battery is connected

Ground (GND)

Powered only when ignition Red/Black (RISK) switch is in "Start" position

From generator (GEN) Red (R) Charging Voltage to battery

Generator (GEN) warning light and

field energizing circuit

Ground (GND)

Color

Wire

Black/Yellow

Brown (BR)

(BKIY)

86 87

Power-input(+) side

Relay change-over contact

switching relay

vi How to read wiring diagrams I

General

Information l

Wire Color-Code

BL BR CL

GY LT.G OR

v w

Black Blue Brown Clear Green Gray Light Green Orange Red Violet White Yellow

Connectors

............................................................................. Single-point

T2 ........

T3 ......................................

T4 ..................................................................................... 4-point

T6 ..................................................................................... 6-point

T8 ..................................................................................... 8-point

T12 ............................

T26 ................................................................................. 26-point

Each connector has a unique number.

T6b are three different 6-point connectors.

....

..............

....

..................................................................... 2-point

...

..........................................

......

.............................................................

................................................... 12-point

Example: T6, T6a and

3-point

1 0-point

Combined codes indicate a multi-colored wire. Example: The code

tracer stripe.

Note

Sometimes the wire color on the

the one on the wiring diagram. Don't be concerned, sure to confirm that the wires connect to the proper

terminals.

Wire Size

The wiring diagrams in this manual identify wires by their metric wire size. Metric wire sizes indicate cross-sectional area in square wire sizes and their (AWG) sizes.

(Cross-sectional

R/G

indicates a red wire with a green

car

may be different than

millimeters (mm

equivalents in American Wire Gauge

Metric size

area-mm

0.35

0.5

0.75

1.0

1.5

2.5

4.0

6.0

16.0

25.0

35.0

The table below lists metric

American

)

Wire Gauge

(AWG)

22 20 18 16 14 12 10

2 2

just

Wiring diagrams terminal. Example: T3a/2 is terminal two of connector T3a.

T3a

usually also identify a particular connector

1 2 3

(T3a/2)

I 96-902 I

I General Information I How to read wiring diagrams vii

2. Test Equipment

2.1 LED Test Light

Special Tools

The most basic electrical troubleshooting calls for specialized electrical cians do this work using Special Tools, many of which are designed specifically for working on Proper tools are essential to ensure accurate test results and

to The Special Tools shown in this manual are identified by the

order numbers that can be used to special-order the through your authorized dealer Parts Department.

test equipment. Dealer Service Department techni-

electrical systems.

prevent damage to sensitive components.

tools

A test light simple electrical tests that would otherwise require a multimeter. It lights to indicate when there is Voltage potential between any two test-points in a circuit.

With one probe contacting the battery a known ground (GND) connection, the other probe can be

used to check for test light will light when the test probe contacts a Voltage source, and current flows from the Voltage source to ground (GND).

With one probe contacting a known source other probe can be used to check for continuity to ground (GND) at other points in the circuit. Current will flow and the

test light will light when the test-point provides the known Voltage source with a path to ground (GND).

Caution

A common test light (with incandescent bulb) longer be used. sensitive electronic components.

inexpensive tool used

Voltage at other points in the circuit. The

The

bulb's high current draw will damage

perform many

negative(-)

terminal

Voltage, the

may

viii

Test equipment I General Information I

LED Test Light (US 1115)

Used to check for Voltage reaching components or when searching for malfunctions in a circuit.

Voltage range: 3 to 48 VDC

CAUTION

A common test light (with incandescent bulb} may no longer

used. The bulb's high current draw will damage

sensitive electronic components.

LED Tester (VAG Order Number: TAG 152

Two-pole Voltage tester with two LEOs (light emitting diodes),

suitable for measuring from 3 to 48 Volts

When used to test

LED will light, depending on polarity. When used to test AC

circuits, both LEOs will light.

Supplied with banana clip and detachable probe-can

directly with VAG 1598 Test Box.

For troubleshooting all common electrical and electronic components in automobiles. Safe for testing electronic components and circuits because of extremely low current consumption (1.5

15278)

circuits, the

rnA

maximum).

780

ZEL

positive(+)

or AC.

negative(-)

used

Note

This tool has been superseded by Special Tool

15278, LED Tester. (US 1115 is still considered an

acceptable equivalent

VAG 15278).

VAG

Voltage range: 3 to 48

CAUTION

A common test light (with incandescent bulb) may no

longer be used. The bulb's high current draw will damage sensitive electronic components.

Volts (AC

DC)

Note

This tool supersedes Special Tool US 1115 LED Test Light.

I General Information I Test equipment

Making an LED Test Light

A lower-cost alternative to buying an LED Test Light such as US 1115 or VAG 15278 is to make one, using parts from most any electronics supply outlet.

Assemble the components as shown. Use needle nose pliers to hold the parts and to act as a heat dam while soldering. Insulate electrical tape.

the connections with heat-shrinkable tubing

1/4 watt, 3300hm resistor

available

2.2 Multimeter or Volt/Ohm Meter (VOM)

A multimeter or Volt-Ohm meter (VOM) is used to measure

Voltage, resistance (Ohms) or current (amps or millamps) . Two types of meters are in common use. The analog or swing-needle Volt-Ohm meter displays test values according to the position of a multimeter shown here and recommended are

Accuracy is an important consideration when choosing a meter. Analog or for accuracy as a percentage of

typical analog meter may be rated as accurate to ± 3% of

A full scale. Some analog meters offer 1 0-Volt and 50-Volt scales, electrical systems, this means testing on the 50-Volt scale,

with a corresponding decrease in accuracy. scale, ± 3% accuracy is equal to ± 1.5 Volts. While still useful for testing circuits such as may not be accurate enough for use where precise ments are required.

displays test values as numbers. The meters

with no range in between. For 12-Volt automotive

needle on the meter face. A digital

digital multimeters.

swing-needle Voltmeters are generally rated

full-scale on the meter face.

On a 50-Volt

lights and horns, analog meters

measure-

Do-it-yourself LED Test Light for safely testing sensitive state circuits.

Parts:

LED(1)

1/4 watt, 330 0 resistor (1}

Alligator clips (2)

4. Wire,

5. Heat-shrinkable tubing or electrical tape

Solder and Soldering Iron

solid-

Digital multimeters are preferred for precise measurement and for electronics work because most more accurate then most of

digital multimeters is that they are less likely to be misread, since there is no distorted by reading at

Perhaps the most important consideration is input impedance-

how much of a load the meter places on the circuit being tested. Meters with

the circuit because they allow more current flow through the meter. This can exceed design sensitive electronic components.

Most

digital multimeters have very high input impedance-1 0 megohms (10,000,000 ments while allowing very little current flow through the meter. The meter induce damaging current

needle position to

itself is not a load in the circuit, and does not

analog meters. Another advantage

angle.

low input impedance place a greater load

or higher-and make their measure-

flow.

digital multimeters are

misinterpreted

limits and be damaging to

x Test equipment I General Information I

Multimeter Kit • digital (US 1119, VAG 1526) Order Number:

TU1119

000 00 KTM

Fluke sa• Digital Multlmeter Order Number: TFL UKE 830 00 RSE

Used for monitoring electronic engine controls (Example: setting/checking the idle speed control system) and for general

electrical troubleshooting.

Note

Used for monitoring electronic engine controls (Example: setting/checking the idle speed control system) and for general

- 1

- ± 0.3%

- fully overload-protected

electrical troubleshooting.

0 Megohm input impedance

Voltage accuracy

This tool has been superseded Multimeter.

acceptable equivalents).

(US 1119

VAG

the Fluke

1526 are still considered

83"

Digital

Note

This tool supersedes Special Tool US 1119 Digital Multimeter Kit.

General

Information

I Test equipment

2.3

Adaptor Kit (VW 1594)

Order Number:

Used to connect electrical measuring equipment to various harness connectors in the electrical system.

Test Kits

CAUTION

TV1

594 400 97 KTM

Test Box (VAG 1598) Order Number: WAG 159 800 00 VOA

Used

perform static and dynamic tests of electrical and electronic systems without damaging miniature contacts, especially where limited access to connectors makes testing difficult.

Test connections made carelessly can damage harness connectors, causing tions

and

future problems.

without proper tools

poor

connec-

~~-~

·-

Ell

U!J

xii

Test equipment I General Information I

Tester (VAG 1466)

Used

systematically troubleshoot electrical circuits.

2.4 Computer Memory Saver

Used on vehicles with theft-protected radios

radio from disconnected. Use of this activate the radio (reenter the correct code) after reconnecting battery power.

WARNING

Always separate the airbag Voltage supply connector before using a computer memory saver. Failure to may information, see the Circuit Section in this manual entitled Airbag,

electronically locking when battery power is

tool eliminates the need to re-

result in accidental activation

see the Repair Manual.

prevent the

the airbag.

For

Snap-On Computer Memory Saver Part No.

Y A960

Home-made computer memory saver

j91-A051I

l91-A052j

General

Information I Test equipment

xiii

Handling Components

and

Connectors

Harness Connectors

The harness connectors used throughout the vehicle are designed to positively shown

release the connector.

CAUTION

disconnect,

on the wires themselves.

Typical wiring harness connector. Push on wire lock (arrow) and

gently

pull

on connector to release.

lock into place. Press on wire lock as

pull

only on the connector body. Never

pull

I91-A051I

Making Test

Many electrical troubleshooting tests will require hooking up to wiring harness connectors, electrical components. Test connections made carelessly without proper tools can easily damage the connectors, causing poor connections and future problems.

To avoid connector damage, test connections to wiring

harness connectors must be made using

terminals which will mate properly with the connectors . The

Special Tools recommended include special adapters which

can be used to make test connections connector damage. See 2. Test Equipment.

All test connections to harness connectors should be made using the proper adapter will not deform the connector cavities.

Connections

socket connectors

small, flat-blade

safely and prevent

correct size flat connectors that

Alligator-clip (Part Number: N 17

test

457

leads

with

flat

connectors

xiv Components and connectors I

General

Information

Wiring Harness Repairs

When repairing wiring harnesses, use only high-quality electrical connectors suitable for use with electronic compo-

nents.

To make connections, use crimping pliers that make a "W"type crimp. Only this type of crimp provides the necessary

mechanical strength .

197-Mool

I97-A402I

Wire

crimping pliers, used

Connector repair kits, connectors and the correct crimping pliers are available through your authorized dealer Parts Department.

make "W"-type crimps.

Typical "W"-type crimp connection

Typical wire crimping pliers,

crimps.

not

I97-A4o11

suitable for making "W"-type

General

Information

I Components

and

connectors xv

4. Troubleshooting

4.1

Electricity is defined

Current and Resistance.

Voltage

Voltage referred to as difference in potential (potential for the flow of electricity) between any two points in a circuit.

A typical automobile battery, for example, has a difference in potential of about 12 Volts between the positive(+) terminal and the negative

The basic units of electrical potential are Volts (V). Very low Voltages are expressed as millivolts (mV).

1 V = 1000 mV; 1 mV =

Current

Basic Electricity

three basic elements: Voltage,

a measure

electrical "pressure". It can be described as the

electromotive force, sometimes

(-)terminal.

.001

Resistance vs. Current Flow

The basic rule of electricity (Ohm's Law) states that one unit of force flow against one unit of resistance Law, we also know that:

When electrical system, current and resistance affect each other. As

lower resistance will permit higher current flow. Higher resistance = lower current flow

Example: Corrosion on a headlight connector (higher resis-

tance) causes the light to

Lower resistance = higher current flow

Example: resistance) overloads circuit capacity (higher current flow) and blows a fuse.

Volt) is required for one unit of current

Ohm). From Ohm's

Voltage

resistance increases, there will be less current flow. And

A damaged wire shorted to ground (GND) (lower

= Current x Resistance

approximately constant, as in

dim (lower current flow).

am) to

automobile

Current is the term describing the conductor. current to

The basic units of current

Small amounts of current flow are often measured in

millamps (rnA).

Resistance

Resistance resists or opposes the flow of electricity. Conductors are made from materials of low resistance that allow electricity to flow easily . Insulators are materials of very high

resistance that inhibit the low of electricity. The basic unit of resistance is the Ohm

values are often expressed as Kilohms

1 KO =

In a complete circuit, potential (Voltage) will cause

flow from positive(+) to

flow are amperes or amps (A).

1000mA; 1 mA=.001

10000

flow of electricity through a

negative(-)

High resistance

(Knr

i Troubleshooting I General Information I

Definition of a Circuit

Open Circuits

Four things are required for current to flow in any electrical

circuit, and for that circuit, and

intended:

- Power Source (Voltage)

- Conductors (wires, printed circuits, etc.)

- Load or Consumer (a user of electrical power)

- Complete Circuit (a connection to ground [GND])

Battery (Power source)

for

that circuit to function as

An open circuit is

occurs when some kind of malfunction interrupts the circuit path and prevents current open circuits are:

- broken wire

- loose

- corrosion

- malfunctioning fuse or component Test for

Ohmmeter (multimeter), points of the circuit using a test See 4.4 Checking Wiring and Components.

Short Circuits

A short circuit is an unintended complete circuit. A short circuit occurs when some kind of malfunction causes current

flow to follow the wrong path.

A short circuit to ground (GND) (grounded circuit) may prevent Voltage from reaching a component. If Voltage is shorted

directly to ground (GND), bypassing any load, the unrestricted current flow will damage fuses wires common causes of short circuits are:

- damaged wire

or or

incomplete circuit. An open circuit

flow. Some common causes of

disconnected connector damaged connector terminal

open circuit by checking continuity using an

checking for Voltage at various

light

Voltmeter (multimeter).

components. Some

wiring harness

Ground (GND)

(Car body)

A complete circuit

B029ELG

- malfunctioning insulation

internally damaged component

- incorrect connection Test for a short circuit to ground (GND) using a multimeter or

a test light to indicate circuit malfunctions and abnormal current flow paths. See 4.5 Checking for Short Circuit to

Ground (GND).

I General Information I T

ubleshooting

xvi

Troubleshooting Procedure

Working on the Electrical System

Verify the

stand the happens. Check all functions of the system and note the symptoms before starting any testing

complaint-

problem. If possible, let the driver show you what

Check the complaint. Try to under-

disassembly.

Analyze the problem - Identify the part of the electrical

system that is most likely to be causing the problem. Find the Circuit Section in the manual that applies to that part of the system. Find the wiring diagram that By following the circuit from a ground (GND) back to the

power source, get

Find the

simple and logical step-by-step procedure. Test portions of the circuit one at a time, starting with he area or component most can reach most easily.

Repair the

problem, make the repair. Use appropriate tools and proce-

dures.

problem-

likely

be malfunctioning. Test first at points that you

problem-

understanding of how the circuit works.

You will find the problem if you follow a

When you find the cause of the

applies to the vehicle.

Check the results - Be sure it works. Check the functions of

all parts of the circuit that you worked on.

A test light circuits. See equipment.

Current flow is logical, always moving from the highest potential at the Voltage

at ground should start with the ground (GND) and then follow the wires

back to the source of power.

a multimeter can be very helpful

for

2. Test Equipment for more information

source(+)

(-).

Using a wiring diagram to trace a circuit, you

toward the lowest potential

testing

test

To troubleshoot a circuit:

1. Inspect all connections, especially grounds (GND). Make sure they are

2. Check the fuses.

Note

Repeated fuse failures are the sign wire, a failed component, somewhere in the circuit.

3. Check for in

the circuit.

4. Check continuity between points to look for breaks in the circuit (open circuit).

clean, tight and corrosion-free.

a malfunctioning

a short to ground (GND)

Voltage reaching particular components

points

Check Voltage drop at connections, especially ground (GND) connections.

xviii Troubleshooting I General Information I

4.2 Checking for voltage

Checking for Voltage confirms that the circuit is uninterrupted between the Voltage source and the test point. The example illustrates troubleshooting the high-speed circuit for

the radiator cooling fan .

Voltage: If the test light

potential, then the circuit between the Voltage source and

terminal 1 of the fan connector is OK.

NO Voltage: Power

probably OK. Look for a malfunction somewhere

fan is between the Voltage source and the fan connector. (Example: Check for Voltage reaching terminal E87La of the fuse/relay panel)

CAUTION

Direct contact with meter probes nals can easily damage the small contacts, causing connections

Special Tools include adapters for making test connections See 2. Test Equipment.

safely

and

multimeter indicates Voltage

not reaching the fan connector. The

the connector termi-

poor

risking future intermittent malfunctions.

preventing

connector

damage.

2.5

RIBK

E87La

t4130

I.~

...

lft/87

E87L

2.5

RIBL

LED Test Light or Multimeter (DC Volts scale)

Ground (GND) or

Battery negative

(-)

159

COOLANT FAN

160

2.5

16.

162

I General Information I Troubleshooting xix

4.3 Checking Ground (GND) Connections

Checking ground (GND) connections as shown confirms that the circuit is complete - that the necessary path to ground (GND) is uninterrupted and current can flow The example circuit

for

Voltage: If the test light or multimeter indicates Voltage,

then there is Voltage source and ground (GND) at the test point. The ground (GND) side of the circuit, between fan connector and battery negative

NO Voltage: The test point is not providing a path that

completes the circuit OK. Look for a malfunction somewhere in the wiring between the fan connector and chassis ground (GND). Also check the mechanical ground connection at the chassis (body).

illustrates troubleshooting the high-speed

the radiator cooling fan.

potential for current flow between the known

(-),

ground (GND). The fan is probably

the circuit.

terminal 3 of the

OK.

1 2

E87La E87L

14130

I~-

,7181'

LED

Test or Multi

meter

(DC

Volts scale)

Battery positive(+) or other known

Voltage

Light

source

159

2.5

RIBK

COOLANT FAN

160

2.5

RIBL

2.5

1'$1

t62

xx Troubleshooting I General Information I

Continuity (approximately 0 Q): Little or no resistance

indicates that there is a continuous conductive path between the

two

test points - the circuit's ground (GND) path between

terminal 3 and battery negative

(-)

is OK.

No Continuity: There is resistance to current flow

ground (GND) side of the circuit. The fan is probably Look

for

a malfunction somewhere in the wiring between the fan connector and chassis ground (GND). mechanical ground (GND) connection at the chassis (body).

CAUTION

direct contact with meter probes nals can easily damage the small contacts, causing connections

Special Tools include adapters for making test connections See 2. Test Equipment.

safely

and

risking future intermittent malfunctions.

and

preventing

Also check the

the connector termi-

connector

the OK.

poor

damage.

1 2

E87La

E87L

Multi (Ohms

Ground

Battery

meter

scale)

(GND)

negative

(-)

-=-

159

2.5

RIBK

2.5

RIBL

COOLANT FAN

1:62

I General Information I Troubleshooting

xxi

4.4 Checking Wiring and Components

Resistance Checking a portion of the wiring harness or a component as

shown indicates whether

tive path - whether current can flow between the two test

points. The example illustrates troubleshooting the Close Throttle Position switch and the Wide Open Throttle Position switch in the fuel injection system .

CAUTION

Resistance measurements always switched always powered (fuse/relay panel "30" circuit for example) disconnect the battery before testing.

Always use a digital (low current) meter. the Ohms scale passing a small amount component being checked.

Improper testing nents.

Continuity indicates that there is a continuous conductive path between the two test points. As shown, this is correct for the normally Closed Throttle Position switch in the Closed Throttle Position (switch not actuated). Also check that the switch opens (no continuity) when actuated by the throttle.

Continuity

not there

made with

OFF

(approximately 0 0):

all

power to the circuit

. When testing continuity in a circuit that is

a multimeter, measures resistance

current through the circuit

may

damage sensitive electronic compo-

a continuous conduc-

and

continuity checks must

Little

no resistance

component

ohmmeter,

Multimeter (Ohms scale)

2 3

0.5

BRIY

•

0.5

T3t3

THROTTLE

WIDE

OPEN POSITION

SWITCH

Continuity: the switch. In the example, this indicates that the normally Closed Throttle Position switch or the wires between it and the connector (t3) are malfunctioning.

There is resistance to current flow through

xxii Troubleshooting I General Information I

CAUTION Direct

contact can easily damage the nections

Special Tools include adapters for making test connections See 2.

with

meter

probes

the connector terminals

small

contacts, causing

and

risking future intermittent malfunctions.

safely

Test

and

preventing

Equipment.

connector

poor

con-

damage

Continuity indicates that there the two test points. normally Wide Open Throttle Position switch ing.

Continuity:

shown, this is correct for the normally Wide Open Throttle

Position switch. Also check that the switch closes, completing the circuit, when actuated switch.

(approximately

In the example, this indicates that the

There is no connection-an open circuit.

0):

Little or no resistance

a continuous conductive path between

the Wide Open Throttle Postion

malfunction-

CLOSED THROTTLE POSITION SWITCH

0.5

BLIW

0.5

Multi

meter

(Ohms

scale)

0.5

BRIY

I General Informati

)®

I Troubleshooting xxiii

Voltage Drop

Checking shown will indicate whether there is abnormal resistance creating an additional load in the circuit - consuming power and dropping the Voltage available to other parts of the circuit.

circuit is powered

Voltage drop across connections or components as

Note

Voltage drop measurements can only be made when the

and

there is normal current flow.

CAUTION

Direct contact with meter probes can easily damage the small contacts, causing nections

Special Tools include adapters for making test connections See 2. Test Equipment.

and

risking future intermittent malfunctions.

safely

and

preventing

the connector terminals

poor

connector

damage.

con-

The example

switch. The switch is in the circuit to switch power to the back-up lights and the switch is closed, it should have very little resistance and not be a consumer.

If dirt

or some of the available battery Voltage goes into overcoming that resistance. Less Voltage

lights, and they will not be as bright.

Note

An ohmmeter can measure resistance (or check continuity) only when the circuit is almost no load.

illustrates troubleshooting the back-up light

On and Off. When Reverse gear is selected

corrosion on the switch contacts creates resistance,

available

not

powered, i.e. when there is

light the back-up

xxiv Troubleshooting

General Information

+ 230 hidden pages

Audi 90 1993 Service Manual/electrical Wiring Diagrams

Specifications and Main Features

Frequently Asked Questions

User Manual