Factory Automotive Wiring Diagrams

Factory Automotive wiring diagrams or electrical schematics are a fantastic way to help one navigate through a wiring job or any type of wiring diagnoses on a vehicle.  Sometimes an automotive wiring diagram is needed for something as simple as wiring in a car stereo or something as complicated as installing an engine wiring harness.  What ever the case may be, factory automotive wiring diagrams are an essential tool for getting the job done.  Have you ever tried to do a wiring repair with more than a few wires without a wiring diagram?  It can be very difficult.  Using a wiring diagram saves you time and money.

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Where to get Automotive Wiring Diagrams and Schematics

While there are many sources on the internet that you can get your hands on factory automotive wiring diagrams and schematics, there two places that I have found reliable without a doubt.  They are Alldata and Mitchell on Demand.  Both are a small one time fee but both have very good customer support that will help you locate the correct wiring diagram and repair information your looking for within their system.  Sometimes you can Google certain wiring diagrams but I have found they never come back accurate.  There are so many variables that can affect the wiring diagram you don’t know if it is reliable or not.  It just pays to know you are using the right wiring diagram.

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How to read Automotive Wiring Diagrams and Schematics

There are a lot of things to consider when looking at automotive wiring diagrams or electrical schematics.  I will start with the absolute basics.  The top of the wiring diagram usually indicates where the “power” is coming from for the specific component.  For example, if you are looking at a wiring diagram for a fuel pump, the power source is going to be at the top of the page.  Either a relay, fuse or the power distribution center where the electrical component gets its power.  Most of the time, if you are looking at a power distribution wiring diagram, the power source will be located at the top of the page.  Main fuses or even battery supply.  The bottom of the page is the Ground for the specific component.  Sometimes components will share a common ground and sometimes they will not.  Assuming all of the grounds are good, they will all eventually lead back to the same place.. the battery.

In some cases the diagrams are laid out so it goes from the left to the right.  (Some Toyota wiring diagrams are laid out this way).   This is usually not the case but it does happen and it is very easy to read.  (I think I even prefer it this way)

Here is a good beginners guide to reading schematics.  They also have an E download for your kindle as well.

Factory Wiring Schematic Symbols

Here is a picture of some symbols you will see when looking at an automotive wiring diagram. Some are very common and some are not so common. If you look at the top row of the picture, you will see a symbol of a battery, fuse, circuit breaker and fusible links. These are all very common and it is important to know what these symbols are. You will also see an two arrows (one on top of another) which indicates a connector. Then it is followed up by a number assigned to it by the manufacturer. For example, C123 is connector 123. This make it easy to locate the connector, find a pinout chart for the connector if needed and even order a new connector from the dealership if by chance if needs to be replaced.  Also, on this picture, you will see a symbol of a ground, clockspring, open and closed switch, oxygen sensor, resistor, one speed electric motor, two speed electric motor, reversible electric motor and more.

Common Symbols you will see on a wiring diagram

Automotive wiring diagram Acronyms

Here are some common Acronyms you might see when looking at an automotive wiring diagram. The picture is specific to Dodge, Jeep and Chrysler vehicles. Some common ones I see every day when looking over wiring diagrams or electrical schematics are PCM, SKIM, PCI BUS (which is the communication networking between all modules on board the vehicle), PS, PSP, VSS, OSS, TRS, PDC and more.

Common Dodge, Jeep, Chrysler Acronyms

Voltage check

Connect the black lead of a voltmeter to a known good ground and then connect the red lead of the voltmeter to the selected test point and take a reading.   It is as simple as that.  I recommend an Auto-Ranging Fluke Digital Multimeter.  If you have a manual setting meter, it needs to be set to the 20 volt DC scale.  Depending on the circuit you are testing, the ignition switch may need to be turned “ON” to get a voltage reading.   The voltmeter will display the difference between the two leads.   For example, taking a voltage reading at the battery with it fully charged at 12.6 volts, the the voltmeter will display the difference between the positive and negative post or terminal and will display the 12.6 volt reading.

Continuity Test

Checking for continuity should always be done when there is no voltage within the circuit.  For example, the circuit not in use or even with the battery disconnected.  Remove the fuse for the circuit being checked or disconnect the battery.  Connect one lead of the ohmmeter to one side of the circuit being tested.  Connect the other lead to the other end of the circuit being tested. Low or no resistance means good continuity.

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Checking for A Short To Ground

Remove the fuse and disconnect all items involved with the fuse.  Connect a test light or a voltmeter across the terminals of the fuse.  Starting at the fuse block, wiggle the wiring harness every 6 to 8 Inches and watch the voltmeter/test light.  If the voltmeter registers voltage or the test light glows, there is a short-to-ground in that general area of the wiring harness.

Voltage Drop testing

Connect the positive lead of the voltmeter to the side of the circuit closest to the battery.  Connect the other lead of the voltmeter to the other side of the switch or component.  Operate or turn “on” the electrical circuit.  This will “load” the circuit.  Remember, the voltmeter will show or display the “difference” in voltage between the two points.   So if the circuit is good and there is no loss of voltage when the circuit operates and the voltmeter will display a reading of 0 volts.   However, if there is a bad connection preventing the circuit from working, the voltmeter may display a reading of 12 volts or battery voltage.  Any reading above 1 or 2 volts is considered “bad” or “too high” when doing a voltage drop.

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If you want to become a pro at reading automotive wiring diagrams, here is a great training course on how to read wiring diagrams. In this video, they talk about common symbols, point diagnoses, understanding location codes and connectors as well as using O.E.M and aftermarket automotive wiring diagrams. Click Here for Automotive troubleshooting secrets!   It even has a dedicated section just for Automotive wiring diagram tips.

Chrysler wire Colors Codes

BL = Blue
BK = Black
BR = Brown
DB = Dark Blue
DG = Dark Green
GY = Gray
LB = Light Blue
LG = Light Green
Or = Orange
PK = Pink
RD = Red
TN = TAN
VT = Violet
WT = White
YL = Yellow

Ford wire Color Codes

BU     Blue
BK     Black
BN     Brown
DB     Dark Blue
DG     Dark Green
GN     Green
GY     Gray
LB     Light Blue
LG     Light
YE     Yellow
NA     Natural
WH     White
TN     Tan
SR     Silver
RD     Red
VT     Purple
PK     Pink
OG     Orange

Nissan wire Color Codes

B = Black
W = White
R = Red
G = Green
L = Blue
Y = Yellow
LG = Light Green
BR = Brown
OR or O = Orange
P = Pink
PU or V (violet) = Purple
GY or GR = Grey
SB = Sky Blue
CH = Dark Brown
DG = Dark Green

Toyota wire Color Codes

B = Black
W = White
BR = Brown
L = Blue
V = Violet
SB = Sky Blue
R = Red
G = Green
LG = Light Green
P = Pink
Y = Yellow
GR = Gray
O = Orange

Honda Wire Color Codes

BLK = Black
BLU = Blue
BRN = Brown
GRN = Green
GRY = Gray
LT BLU = Light Blue
LT GRN = Light Green
ORN =  Orange
PNK = Pink
PUR = Purple
RED = Red
WHT = White
YEL = Yellow
NAT = Natural

Wiring diagrams for the following systems..

Antilock Brakes / Traction Control Systems, Brake Warning Indicator, Cruise Control, Heated Glass Element, Heating and Air Conditioning, Instrument Panel, Gauges and Warning Indicators, Lighting and Horns, Mirrors
Power Locks, Powertrain Management, Radiator Cooling Fan Motor, Radio, Stereo, and Compact Disc, Seats, Starting and Charging, Trailer Adapter Kit, Transmission and Drivetrain, Windows, Wiper and Washer Systems

Ford factory wiring diagrams and electrical schematics

GM/Chevy factory wiring diagrams and electrical schematics

Chrysler factory wiring diagrams and electrical schematics

Toyota factory wiring diagrams and electrical schematics

Honda factory Wiring diagrams and electrical schematics