All modern vehicles have a computer or the ECM (Electronic Control Module) that controls the operation of the vehicle power train (the engine and transmission). The main purpose of this is to keep the engine running at top efficiency with the lowest possible emissions.
The engine parameters need to be constantly and precisely adjusted according to various conditions such as speed, load, engine temperature, gasoline quality, ambient air temperature, road conditions, etc. That’s why today’s cars have much more electronics than in early days – there are a large number of various sensors and other electronic devices that help the vehicle computer or ECM to precisely control the engine and transmission operation and monitor emissions.
The vehicle computer system has self-testing capability. When the computer senses that there is a problem with some of the components it stores the corresponding trouble code(s) in its memory and lights up the “Check Engine” or “Service Engine Soon” light to tell you that there is a problem and your car needs to be looked at. To properly diagnose what is wrong, you need to take your car to an automotive shop with diagnostic capabilities. The technician at the repair shop will then hook up the scanner to the car’s computer and retrieve the stored trouble code(s). Then he (she) will research the code(s) present in an automotive specific network for common failures. The technician uses this research along with his (her) knowledge to form a game plan for the repair process.
The code itself doesn’t tell exactly what component is defective – it only indicates where to look, what engine parameter is out of normal range. The technician will have to perform further testing to pinpoint a defective part, faulty wiring or connections related to the specific circuit. This process varies depending on the complexity of the circuit and vehicle. Precision Automotive constantly upgrades software and has factory software for a number of import and domestic vehicles.