Diagnose check engine light
Check engine light diagnosis tips and helpful hints from a Master auto mechanic. Learn not to panic and what to do when the dreaded light pops on.
One of the most common car questions I receive as an ASE certified technician is why is my check engine light on. This is a simple question that may have a complicated answer. The check engine light may be on for a thousand different reasons. One reason related to each possible code that the computer would set. The vehicle manufacturers, along with the federal government have made this check engine light warning system very sensitive.
A minor malfunction, or even an intermittent problem or temporary glitch can turn on the check engine light. Unfortunately, if the problem is intermittent or a temporary malfunction that disappears the light will remain on.
The check engine light will have to be reset. The best way to approach this is to buy an inexpensive automotive scan tool and plug it into your diagnostic connector on your vehicle. You can then read the code and record it before a erasing it. Now that you have the code and the definition recorded. You can clear the check engine light and drive the vehicle to see if the light comes back on.
If the light does not come back on, it must've been an intermittent malfunction. So now you have just fixed your own car in a matter of a few minutes. But what happens if the light does come back on.
Now you can reconnect your automotive scan tool and check the trouble code again. If the same code has been reset, then it is safe to say that the malfunction is a hard failure or a problem that needs diagnosing. At this point, you can go to routes.
First you can take the vehicle into an auto repair shop and supply them with the information you have gathered. Supplying the code number and the definition will help cut down the diagnostic time of the repair center and save you money. It will also make it clear to the shop that you are an educated consumer when it comes to check engine light diagnosis.
You can also attempt to diagnose the check engine light on your own. Each specific check engine light code will have its own separate path of diagnosis. A good automotive repair manual will provide step-by-step instructions and pictures to support your check engine light diagnosis.
Diagnosing Check Engine Light Table of Contents
Car repair topics covered on this page
- Check engine light video
- What is a generic trouble code
- Laptop Auto Scanner
- Check Engine Light Repair Videos
- Diy check engine light video comments
- Diagnose your own check engine light
- MasterTechMark Videos on You Tube
- Check engine light diagnosis
- Gas prices my opinion
- Evaporative Code Leak Diagnosis
- Check engine light problems
- Diagnose check engine light tools
- Diagnosing the check engine light
- Auto Repair Featured Lenses
- Diagnosing check engine light Feedback
- Search my check engine light content
- My automotive information blog
- Marks favorite hobby
Check engine light video
The gas cap code
What is a generic trouble code
Generic OBD 2 codes
When your scanning your vehicle with a basic scanner it will only read the generic trouble codes. These are by far the most common to set in a computers memory. But you may get a curve-ball known as the manufacture specific code. This a special model or option code that is vehicle specific only. You may find a auto repair bulletin for your vehicle that will aid in diagnosis and repair. But do not worry because it is rare to see these.The codes you will see most often are known as generic diagnostic trouble codes since they are the same for every vehicle. The number one indicates manufacturer specific codes. These diagnostic trouble codes are part of the manufacturers influenced diagnostic software and varying between vehicle manufacturers.
The second digit in the diagnostic trouble code identifies the system, where the malfunction is occurring. The last two digits correspond to a specific code definition.
OBD 1 and OBD 2 are similar in that both systems checked sensor and actuator circuits for opens shorts and out of range values. However, the failure limits for OBD one are far more forgiving, since a circuit or component must fail completely before the check engine light is illuminated or a diagnostic trouble code is stored.
In contrast OBD 2 use a series of monitors or diagnostic tests that conduct performance evaluations on an emission components. Also note that obd II codes have to be reset manually and your check engine light will stay on until you perform this procedure.
If your interested in learning what the 5 digit code stands for I have a report that breaks it down. Learn what each digit stands for in any diagnostic trouble code.
Laptop Auto Scanner
Use your laptop like a scan tool
Introducing a laptop auto scanner with bluetooth technology. If you already have a Laptop computer then this is most likely the most powerful way to diagnose and repair your engine light. The big advantage to using an OBD 2 interface on your laptop is the amount of information you can display at one time.This allows you to compare multiple streams of data during the fault period and this could be key in finding the failed component quickly. The Scan tools weak spot is they only display a few lines of Data. Don't get me wrong the hand held scanner is still what I use the most. This is mainly because I do not own a laptop or PDA.
My repair shop purchased the blue tooth version of the leading obd laptop auto scanner. I have used it several times and it is fun and powerful. You can read about the installation process and whether this wireless option is worth the extra money over the standard scan tool interface. You can read the full report on my YouFixCars.com website and see if this laptop auto scanner is right for you.
Check Engine Light Repair Videos
Watch the video And compare my answer
Leave your thoughts and comments below the diy car repair video.
Diy check engine light video comments
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Diagnose your own check engine light
Anyone can fix their own car with a good manual
Diagnostic charts make it easy to fix your own check engine light. You look up the individual code set and you will find an easy to follow tree chart to help you pinpoint the cause of the problem.The new online diagnostic charts from Mitchell reduce the costs of having the auto repair information you need to less then 10 dollars. Turn off the check engine light for good without having to buy a car repair manual you may never use again!
MasterTechMark Videos on You Tube
Online Auto Repair Manuals
This video shows you what the Mitchell online auto repair manuals look like on the other side of the log in button. More information about this auto repair help program is available at http://www.auto-facts.org/auto-repair-online.html
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Check engine light diagnosis
OBD-II & ELECTRONIC ENGINE MANAGEMENT SYSTEMS TECHBOOK (Haynes Techbook)
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A50.3 OBD II-Fixing Cars Using OBD II (Understanding & Using Obd II)
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OBD II Fault Codes Reference Guide
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DA 50 Understanding & Using OBD II
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OBD II Diagnostic Secrets Revealed (Secrets Revealed series)
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Gas prices my opinion
Back in the 70s when OPEC learned how to flex its economic muscles, U.S. consumers demanded alternative fuels. A few years later when the crisis eased and we got accustomed to higher prices, the idea waned.Once again, we're discovering that the need for alternative fuels is an important way to reduce dependency on OPEC oil. Alternative fuel made from corn or other agricultural products not only can reduce fuel prices but also provides a new market for America's farmers. With alternative fuels, farmers could become the new OPEC, providing fuel to an increasing world market. I put together a page about the 08 gas saver guide I purchased that had a lot of good information on the fuel saving subject.
Evaporative Code Leak Diagnosis
A very common code that can be intermitent
Auto Repair Evaporative Code Leak Diagnosis - OTC Tools
Using the OTC Genisys scan tool to check the service engine soon light and the OTC LeakMaster smoke machine to find an evaporative leak at the fuel pump on a 2001 Jeep Cherokee; evaporative leaks can be hard to find without the right test equipment. These tools and other code readers and scanners are available at http://www.denlorstools.com/home/dt1/page_13031/evaporative_leak_detection___evap_smoke_tester_use.html with free shipping.
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Check engine light problems
Diagnosing the check engine light
Check engine light diagnosis can be challenging. Too often I find technicians, mechanics and the general public wanting to jump in and replace the sensor, simply because the code has been set, in memory. When you set a specific check engine light code. The computer is directing you to a circuit malfunction.This could mean that the sensor involved may need to be replaced, but it also may indicate that there is a problem with the wiring between the sensor and the computer, or that the sensor is reporting a legitimate malfunction.
Let me give you an example of check engine light diagnosis gone bad. Let's say that you have set a diagnostic code for a coolant sensor circuit malfunction. You break out your trusty scan tool, and you find that the sensor reading does not match the engine temperature. In this instance, you may be tempted to jump in and replace the coolant temperature sensor. This may be premature.
Maybe the cooling system has a leak and the coolant level has become lower than the mounting location of the sensor. Without the coolant sensor actually touching the coolant erroneous readings can cause the computer to turn on the check engine light and set a code for this malfunction.
Another point to make is that the coolant sensor can be tested. The sensor can be removed and plugged back into the harness; you can then dunk the coolant temperature sensor into ice-cold water and note the readings that are returned by the sensor.
You can then take that same sensor, and dip it in boiling hot water. And again, note the sensor reading. This is a quick and easy way to find out if the sensor is the reason that your check engine light is on.
Check engine light diagnosis takes time and patience. It is much better to spend a little time doing it properly then going out and buying and replacing sensors that are not returnable. You can visit the next text links for more information on check engine light diagnosis and reading automotive scan tool data.
Diagnose check engine light tools
Equus 3120 Innova Diagnostic Code Scanner with Freeze Frame Data for OBDI and OBDII Vehicles
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Amazon Price: $139.10 (as of 11/29/2009)
List Price: $346.80
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Actron CP9150 AutoScanner Diagnostic Code Scanner Kit (Includes CP9145 Base Scanner, OBDI & OBDII Cables with Hard Case)
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Amazon Price: $155.44 (as of 11/29/2009)
List Price: $582.99
Used Price: $146.99
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Extech 42540 Mini High Temperature -58 Degree to 1400 Degree Farenheit and -50 Degree to 760 Degree Celsius Infrared Thermometer
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Amazon Price: $169.99 (as of 11/29/2009)
List Price: $169.00
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Diagnosing the check engine light
Information on O2 sensors
In this next example of using an automotive scan tool and reading scan tool data. I'm going to give you a very common code that you could find set in the computers memory.I come across the oxygen sensor voltage low or high code all the time. Many mechanics when they find this code just want to go ahead and replace the oxygen sensors. This may not be the right thing to do.
When you pull this code up on your automotive scanner, the first thing you want to do is reset the code and see if it returns.
If the check engine light has come back on and this code has reset the second thing you want to do is perform some basic check engine light diagnosis. Like a good visual inspection for broken or damaged parts and connectors. Next you will want to read the data stream for the oxygen sensors. Reading scan tool data for this code using the automotive scan tool is a lot easier than you would think.
I have written an interesting article about diagnosing oxygen sensor codes. In fact this article is an example of how an o2 sensor code was set for a common problem on ford vehicles. This actually turned into a full blown recall for this particular code on many Ford models.
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Fetching RSS feed... please stand byMarks favorite hobby
Besides diagnosing check engine light problems
My new favorite hobby is learning how to build profitable web sites. Sure the auto repair business is fun but as I get older it gets harder to slide under the vehicle.This is why I have started learning how to build a car website. If you are up to the challenge and have some knowledge on a particular topic you can do the same. This brings a new way to both enjoy and finance your hobby of choice.
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