Interpretation of scan tool data for most do-it-yourself driveway mechanics is a simple matter of retrieving the code and identifying what the code means. This can not only point you in the right direction but is also considered by many technicians as the first step in a logical path of diagnosis.
When a check engine light comes on, and you connect an OBD II scan tool in most cases you will be retrieving the code and identifying the system the failure is in. It also makes sense to clear it and take a test drive to see if the light returns.
This confirms a hard failure or an intermittent one. If you own an advanced obd 2 auto scan tool you can check for pending codes. You can also pull up the data stream and read the information in real time. I have more about inexpensive scanners I own that can read the data stream at my Automotive scan tool review page.
Lets say a particular automobile sets a code for a coolant temperature sensor malfunction of some kind. You can then read the scan tool data for the coolant temperature circuit in real time.
You will be able to monitor the coolant temperature in Fahrenheit and the change in sensor voltage. If the vehicle is cold you can start it up and let it run. Watch the coolant temperature volts rise slow and steady on the scan tool and look for problems.
This verifies the correct operation of the sensor. If the coolant temperature and voltage remains a fixed value yet the vehicle continues to warm up you may have a dead coolant temperature sensor or bad wiring between the sensor and the computer.
Reading scan tool data gives you insight on what the failure might be. When the dreaded check engine light comes on and the vehicle sets a specific code you can then pull up the data stream for that system on the obd II automotive scanner.
Just because the computer sets a code for a specific sensor does not automatically indicate that that sensor has failed. More often than not the sensor is working correctly and making you aware of a problem with the vehicle. I have an example about the commonly misdiagnosed O2 sensor code.
Another example would be a temperature sensor. If we have set a coolant sensor code and when reading scan tool data the voltage increases as the vehicle warms up. The sensor is working correctly at this time. In this scenario the code may have been set due to a stuck thermostat causing an overheating condition. Or even a stuck open thermostat not allowing the vehicle to reach its proper operating temperature.
This gives you a clear path of diagnosis. The best way to approach the repair of the vehicle that has set a diagnostic code is to use the diagnostic tool in combination with a quality repair manual.
The online auto repair manual will provide step-by-step diagnostic troubleshooting procedures with component location diagrams for that particular failure code. Using these tools together can save you a lot of time and money in replacing unnecessary auto parts.
The obd 2 scan tool is very easy to use in my opinion. In most cases and on the majority of automobiles you will find the OBD connector just left of and below the steering column.
The exact location is usually pointed out in the owners manual as well. After finding the connector simply plug in the diagnostic tool and begin reading the scan tool data. Most scan tools come with cd's that provide a good knowledge base for beginner diagnosis.
obd 2 scan tools like the Actron 9580A above, or the Innova 3030 on the right have really come down in price over the last couple of years due to heavy market competition. Reading scan tool data has become much easier also thanks to the OBD II standardized protocols.
Whats cool about the Actron and why it costs more is it has a Code-Connect button on the keypad that lists probable solutions according to the data on file. it's compatible with OBD-II and CAN vehicles 1996 and newer and includes domestic ABS code coverage. It records and can playback information on screen.
If you learn how to read and use a scan tool on your own car you can use the same exact technique on many cars 1996 and up. My advice is to be the envy of your neighborhood and teach yourself how to read scan tool data.
Service engine soon lights pop on all the time because the systems are so sensitive. Why not be the go to guy for when this common problem occurs? Reading through my other pages on my auto scan tool homepage is a great place to start.
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I posted a short video about using online auto repair programs to fix cars at home. See the clip and my pick for best online auto service manual.
The next link takes you to more articles written on the check engine light subject. See how to use auto scan tools to fix complex car problems.
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