What is Auto Diagnostics Software?

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  • Written By: R. Kayne
  • Edited By: O. Wallace
  • Last Modified Date: 01 October 2019
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Automotive diagnostics software, or auto diagnostics software for short, interfaces with a vehicle's engine control computer (ECU) to provide real-time diagnostics and troubleshooting data. It can reset the check engine light (CEL) in the dashboard, pull trouble codes stored in the ECU, and narrow down potential causes for problems. This software is a useful tool for automotive maintenance.

Virtually all modern vehicles include an ECU, also called an engine control module (ECM), which monitors various sensors located throughout the engine, fuel and exhaust systems. In a fuel-injected engine, sensors feed the ECU 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 not not only made things 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 3 feet (0.9 meters) of the driver's seat, reachable without tools.


This law opened the door for commercial auto diagnostic software tools. These tools come with a dongle or interface cable that connects the OBD-II to a laptop computer with a serial, USB, or wireless Bluetooth® interface. The program interfaces with the vehicle's computer to log sensor data and other real-time parameters. Using the program, the CEL can be reset, trouble codes can be pulled, and potential problems can be diagnosed before ever raising 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 the software particularly useful for logging real-time data. Voltage readouts, oxygen sensor testing, and monitoring of various systems are all possible.

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

For those unwilling or unable to do their own mechanical work, this software can still be used to keep the car's owner up to date about any potential problems the vehicle might be having. It can also help the owner avoid needless repairs when taking the car to a professional mechanic since, by being more informed, he or she has 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. Some basic programs are affordable for most consumers, while those at the professional end of the scale tend to have more features and a higher price tag.


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