Check engine light
The check engine light on cars is a very sensitive warning device. We all know the feeling we get when it comes on while driving. First, all the worst case scenario's come to mind and then in an effort to remain calm we tell ourselves maybe it's something minor. In this quick article I will discuss why the engine light comes on and some methods to turn it off. People tend to be less afraid of something when they understand it completely. This knowledge also gives you the freedom to make an educated decision on what to do next.
The warning light is turned on directly by the car's computer. Most manufacturers call it the PCM. This stands for power train control module. You may find other names for this device but basically it is considered the automobiles main computer. The PCM monitors the many different automotive engine sensors marking the high and low values and changes in this data stream. It then divides the sensors into multiple channels. The computer monitors each channel and compares the data to specifications that are burned in memory. When the service engine soon light is turned on the computer is notifying the driver that one of the channels it's watching is out of the specified range. Check engine light comes on
When this light comes on the car may have set a single code or multiple codes. Just an example of why the check engine light can come on would be an oxygen sensor code. The range of operation that the computer is looking for is between 50 and 800 mV. In this specific example the computer is also monitoring the changes in the voltage. These changes in voltage are referred to as cross counts. A cross count is a measurement of how often the voltage goes beyond and then falls below the 500 mv threshold. If the oxygen sensor returns data that is out of the range of what is considered normal operation the check engine light is turned on to notify the driver of a problem.
Does this mean that replacing the oxygen sensor would turn off the light? The answer is, in many cases replacing the sensor will not turn the light off. The reason the code is set in memory is because the sensor was detected to be out of range. This might be because the sensor is faulty but more than likely the sensor is operating correctly and is out of range due to an air fuel mixture problem. A vacuum leak is an example of something that can cause this issue. This is where diagnosing the malfunction properly will save you time by avoiding replacement of unnecessary parts. Using an automotive scan tool you can view the data stream for the particular sensors related to air fuel mixture like fuel trim or intake air temperature and look for problems. Another rule of thumb when diagnosing an oxygen sensor code is to diagnose all the other set codes prior to the O2 one. This is because the exhaust stream malfunction can be triggered by other failures that effect the amount of oxygen in the exhaust. Check engine light on carsTo review your computer is watching multiple channels and multiple sensors and is simply comparing the real time data with the parameters that have been programmed into the unit.
Above or below these data settings commands the PCM to notify the driver. Often these out of range readings can be either temporary or an intermittent car problem. This is again where the scan tool comes in handy for figuring out why the check engine light is illuminated. Specific codes point you to different areas of the computer controlled emission system that might need diagnosis or repair. You can clear check engine light codes and run the vehicle and see if the service engine light comes back on. If it does, then you have a path of diagnosis related to the codes that have returned.
Do you need an instant answer to your check engine light questions. Get a professional tested mechanic to help you with your specific car problems. How to use car scannersIt can also displays freeze frame data of the vehicle's operating conditions at the time of the fault. There are more than 20 reviews from users of this scan tool on Amazon's website. This is a good way to learn more about this product and if it is right for you. Click on the product link on the left to review the unbiased opinions of the general Diy auto repair public. Amazon's website only allows people who purchased and own the individual scan tool to wright a review. With their mass buying power they are able to offer it for less then many other retail automotive places and expedited shipping is available.
This unit is not as popular because of the price tag but there are still more than 80 reviews of this scan tool at the time of this writing. It's very nice to have a tool that can interface with 25 years worth of cars. One user did slam the product because it would not scan his 1989 eagle talon. This is an odd ball vehicle. The Talon was an early mix of Chrysler and Mitsubishi technology. This scanner will scan many but not all vehicles from 1985 to 2011. The original retail price on the 3140 by Equus was over $450. Now it's selling for around $200 bucks. To me this makes it a good deal! But remember the Equus 3140 supports only Domestic obd1 vehicles. If your vehicle is 96 and up and has a standard obd2 diagnostic port this tool works on both foreign and domestic.
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