Automotive diagnostics software, or auto diagnostics software for short, interfaces with your vehicle's engine control computer (ECU) to provide real-time diagnostics and troubleshooting data. Auto diagnostics software can reset the check engine light (CEL) in the dash, pull trouble codes stored in the ECU, and narrow down potential causes for problems. It can also be a useful tool for automotive maintenance.

Virtually all modern vehicles include an ECU, also called an engine control module (ECM) that monitors various sensors located throughout the engine, fuel and exhaust systems. In a fuel-injected engine, sensors feed the ECU or ECM information that the computer uses to make constant adjustments to fuel and air mixture. When the ECU detects a problem it cannot fix, it trips the CEL and stores a trouble code for later retrieval that points the mechanic toward possible systems or mechanisms involved.

Prior to late 1995, manufacturers tended to have proprietary interfaces for ECUs, proprietary diagnostics protocols and proprietary codes. This was not only difficult for professional mechanics, but also for people who wanted to work on their cars. That changed on 1 January 1996, when every vehicle made in the United States would be required to be standardized in this respect. All vehicles must have an interface to the ECU, called an on board diagnostics II (OBD-II) connector, within three feet of the driver's seat, reachable without tools.

This law opened the door for commercial auto diagnostic software. Auto diagnostic software comes with a dongle or interface cable that connects the OBD-II to the laptop via a serial, USB (universal serial bus), or wireless Bluetooth® interface. The program interfaces with the vehicle's computer to log sensor data and other real-time parameters. Using auto diagnostics software, the CEL can be reset, trouble codes can be pulled, and potential problems can be diagnosed before ever cracking the hood.

Auto diagnostics software is used with the ignition key in the accessory position for some purposes, but the engine can also be running for advanced troubleshooting. This makes auto diagnostics software particularly useful for logging real-time data. Voltage readouts, oxygen sensor testing, and monitoring of various systems are all included functions of auto diagnostics software.

It is important to note that there are three types of OBD-II compliant systems in vehicles today. Auto diagnostics software that can read all three flavors of OBD-II is known as "universal" auto diagnostics software. This software will be more flexible for multi-car families or for future vehicles than auto diagnostics software designed to read just one of the three protocols. Before purchasing auto diagnostics software, check to see what kind of OBD-II system your vehicle has.

For those unwilling or unable to do their own mechanical work, auto diagnostics software can still keep you abreast of any potential problems your vehicle might be having. It can also help you to avoid needless repairs when taking the car to a professional mechanic. By being more informed you have a lesser chance of being ripped off.

There are many companies that sell auto diagnostics software, and prices vary as much as any other type of software. Digimoto sells for under 200 US Dollars (USD), can read all three OBD-II protocols, has a slick interface and a wireless connectivity option. Genisys ConnecTech would be one of the many comparable programs, with software like Pico Automotive Diagnostics at the professional end of the scale.