Auto Diagnostics by Professionally Certified Technicians in San Antonio

How Does a Mechanic Diagnose a Car Problem?

Accurate automotive diagnostics are the first step in properly repairing a vehicle. They often begin with a diagnostic scan, but this is only the beginning. A complete and accurate diagnosis of a car problem involves a great deal more expertise, specialized equipment, and time than simply plugging a generic scanner into the on board diagnostics system and reading the trouble codes. To ensure that your vehicle is repaired completely, as quickly as possible, and without any unnecessary expenses, it is important to find a skilled, trustworthy mechanic to diagnose it.

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In today's automobiles, many systems which used to be purely mechanical are now electronically integrated with several computers and software programs. These computer controlled systems are extremely complex, and therefore require more advanced equipment and specialized expertise to diagnose. At Auto Service Experts, we continuously invest in the most state of the art equipment, highly skilled mechanics, and ongoing training and certifications to remain on top of the rapidly changing field of vehicle diagnostics. Our ASE certified Master Technicians have been providing the highest quality of San Antonio car repair services for over 20 years.

What is an On Board Diagnostic System?

All makes & models of modern cars & light trucks (since the mid 90’s) are required to use a standardized on board diagnostic system. This standardization helps professional car repair mechanics to be able to more quickly diagnose problems on different types of vehicles. On board diagnostic systems store information from the vehicle's computer or engine control module. The engine control module (ECM) is connected to many sensors and microchips which gather information about the operation and performance of various systems within the vehicle including the engine, transmission, cooling system, exhaust system, AC, ignition, and more. If the ECM notices that one of the systems is sending data which is outside of its normal operating range it will make minor adjustments to try to fix the problem. In the event of a problem which the ECM cannot correct, it will cause the check engine light to turn on, and record information about the fault in an internal error log.

Do auto diagnostic scanners diagnose car problems?

Using a scanner, diagnostic trouble codes (DTC) are retrieved from the computer. These codes don’t actually “diagnose” the vehicle’s problem, however. They only lead a technician in the right direction. DTC’s can tell you which system is not operating properly, but they can not tell you why, or what actually caused the malfunction. In other words, trouble codes reveal symptoms of a problem rather than causes of a problem. While you can go to a parts store and have your codes scanned for free, this does not involve a true diagnosis and leads to many parts being replaced unnecessarily.

How can relying on trouble codes alone lead to a misdiagnosis?

One of the most common misdiagnoses involves code P0133 which indicates an issue with the O2 sensor response time. Many times people replace the O2 sensor when this code comes up, but there could be several different causes of this issue (such as an electrical problem or an exhaust leak) which do not require replacing the O2 sensor to repair. This is what is known as “throwing parts at a problem”. This method not only wastes the time and money involved in replacing unnecessary parts but often fails to fix the problem as well. When it comes to car problems, the small initial investment in a proper diagnosis is well worth it in the long run.

What is involved in a complete vehicle diagnosis by a specialist?

Quality auto repair shops use highly specialized scanners & computer software programs which are far more advanced than the handheld scanners used at parts stores. Handheld scanners can only read basic codes and not the proprietary codes of different vehicle manufacturers. Professional auto repair facilities also subscribe to automotive databases which are specific to each different make and model of vehicle. These databases contain extremely technical and specific information regarding the diagnosis of a particular code on a particular vehicle. A skilled technician researches the proper databases to narrow down possible causes of the problem, then follows a set of procedures to pinpoint the issue and test the diagnosis. This ensures that only the necessary parts are replaced, and the problem is repaired completely the first time. Some diagnostics are performed very quickly, such as assessing the need for a brake job or AC service, and others are more in depth such as diagnosing transmission problems.

Why hire an automotive diagnostic expert?

Consider a medical diagnostic. A doctor looks at the patient’s symptoms then runs tests to gain more information, does further research, and finally combines this information with their experience and expertise to determine the cause of, and solution to the problem. You could certainly avoid the doctor fee by looking up your symptoms on the internet, but you would probably find that it would be extremely difficult to pinpoint your problem. This is because most symptoms could be caused by any number of different issues.