The Following is an Article I wrote for Angies list The Check Engine light is one of the most misunderstood topics in modern cars. In this article we will discuss what the light means to you and the proper way to diagnose the actual problem. We will also discuss some of the many myths that surround it. First the light itself, it can be found in the dash of all cars built post 1996 and some prior. But for this article we will be talking about 1996 and newer cars or OBD2 systems. It comes in a couple of forms, “Check Engine”, “Service Engine Soon”, or a small yellow picture of an engine. When this light comes on it indicates that there is a problem with the vehicle, in most cases it is ok to drive it for a short time. If the light is flashing then a condition such as a misfire is occurring that could damage the engine or catalytic converters, in this case you should stop driving as soon as it is safe to do so. On all new cars the “Check Engine” light will come on sooner or later, how do you know what it takes to fix it? Diagnosing the light involves some expensive equipment, an understanding of how the system works, and in most cases a step by step process to figure out what is wrong. The most common myth that we encounter on a daily basis is “The Diagnostic Machine”, we get asked to hook the customer’s car up to our machine and tell them what is wrong. It’s not quite that straight forward, when we pull codes from a car the codes themselves are conditions. The code does not say “replace spark plugs”, Instead it may say “P0300: Random Missfire Detected”, or “P0440: Gross Evap Leak Detected”. These are conditions that the vehicles computer has detected that are outside the parameters that the manufacturer has specified for that vehicle. There are over 3000 generic codes and even more manufacturer specific codes in the modern OBD2 system. Think of these codes as clues, they give the technician a general area to look at. It’s like telling the doctor that your stomach hurts, he has to take that information and perform some tests to figure out if you ate some bad food, or your appendix is about to rupture. When someone at the parts store pulls codes for you they are using a “Code Reader”, most cost $50-$150 and they only supply limited information. They will tell you what the code is, and give some limited data. This is an incomplete picture of the problem, no other tests are performed and the person giving you advise is not a trained tech. Typically the parts guy will suggest what he thinks will fix the problem, but that is like taking medical advice from the checkout person at the pharmacy. At a quality repair shop a trained technician will use a “Scan Tool”, these cost between $2500-$10,000 and will provide much more information as well as vehicle specific tests. Scan Tools are updated regularly with an annual cost of about $1200. For instance if you have a code “P0300 Random Missfire” a code readers information stops there, however a scan tool can look deeper and collect more specific information. This information can then be used to determine a more specific repair instead of spending money on parts that don’t fix the actual problem. The modern vehicle has become a computer on wheels, actually it’s more like 30+ computers networked together with multiple sensors, solenoids and other electronics. We often draw the comparison between a doctor and a mechanic, however human beings are the same now as they were when the medical field started. Cars get more and more complicated every year, and there are many different makes and models. An Automotive Technician has to keep up with all these changes and adapt his diagnostic procedure accordingly. It has gotten to the point that an Engineering degree may soon be a prerequisite for understanding the complex systems involved in diagnosing check engine light problems. We have established that diagnosing a “Check Engine” light can be complicated, requiring expensive equipment, training, and someone smart enough to put all this together to get it right the first time. What should you expect when you take your car in to be repaired? In most cases there will be a fee for diagnosing your problem. The charge not only pays for the Techs time, it also pays for the equipment and the factory information needed to do the job right. After the diagnosis you should be provided with an estimate as to what needs to be repaired. Once the repair is completed the codes will be cleared from the vehicle. When this is done there is another code that is set that will not turn on your light. It is code P1000 “System Readiness”, this code will stay in the computer’s memory until the car has run itself through a series of self tests to confirm that everything is operating as it should. You should know that until these tests are completed and passed the car will not pass an emissions test.
Posted on: Mon, 23 Sep 2013 15:44:50 +0000
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