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KEYWORDS: automobile troubleshooting auto automotive car teaching practicing advice troubleshooter do it yourself OBD computer codes scanner scan tool diagnosis diagnostic diagnostics problem problems methods techniques quick maintenance schedule repair speedy fast efficient diagnostic tools equipment

Welcome to Automobile Diagnostics - "The big picture of Automobile Diagnostics"

By Rev. Bill McGinnis, Director - Internet Church Of Christ -
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Rev. Bill McGinnis is an ASE Certified Automobile Technician
and Night Foreman of a taxicab repair shop in Northern Virginia, now retired.

Automobile Diagnostic & Test Tools at

ALLDATA DIY - Detailed Information Online For Your Particular Car,
including step-by-step directions for solving each Diagnostic Trouble Code (DTC).

When the CHECK-ENGINE light comes on in your car, what does it mean?
Click HERE! to find out.

If you are buying or selling a used car, perhaps you can use our
FREE Automobile bill of sale Bill Of Sale.

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The Big Picture Of Automobile Diagnostics

by Rev. Bill McGinnis, Owner -

Automobile Diagnostics - The entire field of investigation and testing to determine the presence or absence of problems in an automobile, and if there are problems, to determine their causes and possible solutions.

Many successful auto technicians have never actually sat back and thought very much about diagnosis. They have been so busy diagnosing the cars and fixing the problems that they saw no need to spend much time thinking about it. Even so, if you spend a little time and get familiar with a few major concepts, I believe you will find that it was time well spent. You will be well rewarded by understanding the "Big Picture" of automobile diagnostics in a way you may have never thought about before. You will then be able to tackle any kind of diagnostic job with extra confidence. These concepts are nothing more than mental devices we use to understand things. They do not need to conform perfectly with physical reality or with all the possible philosophical niceties. It is good enough for our purposes if they work for us to help us solve our problems. Here are the most important of these concepts, as I see them:

1. NORMAL AND ABNORMAL STATES - Everything about the car is either in a "normal" state or an "abnormal" state. Either the brakes are acting normally or they are not. Either the car is starting normally or it is not. Either the engine is running normally or it is not. Either the oxygen sensor is performing normally or it is not. Either the speedometer is working normally or it is not. Either the tires are in a normal state or they are not. Used in this way, "normal" means acceptable, they way they are supposed to be, okay. "Abnormal" means not acceptable, not the way they are supposed to be, not okay. Every thing about the car, even down to the tiniest little bolt, can be categorized as either "normal" or "abnormal."The purpose of all automobile repair is to correct abnormal states and restore the car to its normal state of operation.

2. NORMAL AND ABNORMAL EVENTS - An "event" is when something happens: a spark plug fires, the brakes are applied, a fuel injector opens, a relay closes, the brake caliper squeezes. An event is a change of state, from one condition to another. A "normal event" occurs when something happens just as it is supposed to happen: the headlights come on when the switch is turned on, the engine valves open and close at their proper times. An "abnormal event" is when something happens that is not supposed to happen: the engine quits unexpectedly, the car fails to stop when the brakes are applied, the alternator makes a funny noise. All automotive complaints can be described and understood in terms of abnormal events: some things are happening which are not supposed to happen, and the driver has noticed them. If all the states are normal, all the events will then be normal, and there will be no complaints. Problems solved!

3. UPSTREAM AND DOWNSTREAM - Any automotive process can be understood as a sequence of related events and states happening over time within a context. The context is all of the other events and states which exist at that moment in time. The earlier events and states in a process are considered to be "upstream" from the later events and states, which are considered to be "downstream." Any abnormal event or state downstream must have been caused by abnormal event(s) or state(s) upstream from it.

4. THE NORMAL PROCESSES - A normal process is one in which all events and states are normal. It is necessary to understand the normal processes in a car in order to recognize and understand the abnormal events and states which may occur and need to be corrected.

5. LEVELS OF ABSTRACTION - Processes can be understood and described in different levels of abstraction. A high level of abstraction is one in which the process is summarized, with very few details. Here is a process description in a very high level of abstraction: "You push on the brake pedal and the car slows down and stops." Here is another one: "You turn the key to the right, and the engine starts." A low-level description of the very same processes might take five thousand words, providing much detail about the operation of the various parts of the automotive systems.

6. CAUSATION - In Automotive Diagnostics, we are looking for the causes of abnormal automotive events, in order to correct them and bring all processes back to normal operation. So we do not need to address the entire philosophical question of "causation," but only those parts of it which we need in order to understand the causes of abnormal automotive events. And this is the main thing we need to know: Abnormal states cause abnormal events. If we correct the abnormal states which are causing our abnormal events, we have solved the problems.

Get your OBD II automotive code readers and other test equipment
here => Automobile Diagnostic & Test Tools at

Air Bag Scan Tools & Simulators - Battery Testers - Code Readers & Scan Tools - Electrical Testers & Test Leads - Emissions Analyzers - Engine Analyzers - Fuel Pressure Testers - Gas Analyzers - Ignition Testers - Lab Scopes - Mechanical Testers - Multimeters & Analyzers - Pressure & Vacuum Testers - Software - Thermometers - Timing Lights

NOTE REGARDING CODE READERS: The CAN Protocol (Computer Area Network) is used in some cars starting in 2003, and it will be mandatory in all USA cars by 2008. Many code readers do not support the CAN Protocol, so if you want to be able to read the CAN-protocol codes, be sure that the code reader you choose is "CAN capable" or "CAN enabled." To be sure, you should carefully read the product description of the exact code reader you are considering, to see that this exact one is CAN-enabled. Some older-version Code Readers may not be CAN-enabled, even though they have the same Model Number as newer versions which are CAN enabled. Buyer beware! Be sure to read the Product Descriptions for the exact ones you are considering from each different seller.

Haynes Techbook: Computer Codes and Electronic Engine Management Systems
The Root Cause Analysis Handbook

Next, below, is a more scholarly treatment of the same subject, expanded, based on the work of British philosopher John Stuart Mill.

The Formal Logic Of Automobile Diagnostics

Including John Staurt Mill's "Methods Of Inductive Inference."

The Formal Logic Of Automobile Diagnostics

Steve Litt's "Universal Troubleshooting Process"

Universal Troubleshooting Process

Here is a book that Steve Litt recommends to help you find the root cause of any problem, automotive or otherwise.

The Root Cause Analysis Handbook-A...

When the CHECK-ENGINE light comes on in your car, what does it mean?
Click HERE! to find out.

Control Of Your Car, Control Of Your Life

In your car, the Automotive Computer controls the various parts to provide smoothe engine operation. But who or what controls the various parts of your LIFE? The Lord Jesus Christ will provide perfect control of all parts of your life if you will only invite Him in as your personal Lord and Saviour. For more information about Jesus and you, please click HERE! When the CHECK-ENGINE light comes on in your car, what does it mean?
Click HERE! to find out.

See Our => Showcase Of Computer Code Readers And Scan Tools <=

You cannot get the OBD II codes without using a code reader or a scan tool (scanner)!
These are our web pages at

Automotive Service Advisor - For everyone who owns a car.
Fix-A-Car - For people who work on their own cars.
Automotive Tools And Equipment - Excellent list for the well-equipped shop.
Automotive Books And Magazines - Books and magazines about cars.
Automotive Art Gallery -
Free Automobile Bill Of Sale -
Scan Tools And Code Readers - "When the check-engine light comes on, what does it mean?"
Automotive Glossary - Glossary of automotive terms.
A General Strategy For Maintaining Your Car -
Automotive Diagnostic Trouble Code Definitions - See what the codes mean.
Automobile Diagnostics - The big picture of Automobile Diagnostics.
Ford Crown Victoria Diagnosis - By e-mail, free of charge. (Crown Vic only)
Selected Automotive Products And Services
Equus CanOBD2 Code Reader
The Formal Logic Of Automobile Diagnostics -
Automotive Tests - Do-it-yourself tests for your car.
AUTO FACTORY MANUALS - Most authoritative, detailed, complete information - where to get it.
Auto Safety Advisor - Practical advice for safer driving and accident reduction.
Tools4Cars - A Website devoted to automotive tools.
Automobile Technician - For the professional automobile technician.
U. S. Government Database: Automotive Recalls And Technical Service Bulletins (TSB's) -

See Our => Showcase Of Computer Code Readers And Scan Tools <=

You cannot get the OBD II codes without using a code reader or a scan tool (scanner)!

ALLDATA DIY - Detailed Information Online For Your Particular Car,
including step-by-step directions for solving each Diagnostic Trouble Code (DTC).

We are a member of the Committee For The Golden Rule

May the Lord bless this presentation of His holy Word.

     Rev. Bill McGinnis  <><

See more pages like this, at our Index of Pearls Of Faith, a treasury of Biblical truths.

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Blessings to you. May God help us all.

       Rev. Bill McGinnis, Director -

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