Modern vehicles are being fitted with more and more electronics. This complicates diagnosis and repair, especially as the individual systems are often interlinked. The work of service and repair workshops is being fundamentally changed. Automotive engineers have to continually update their knowledge of vehicle electronics. But this is no longer sufficient on its own. The ever-growing number of electrical and electronic vehicle components is no longer manageable without modern diagnostic technology – such as the latest range of KTS control unit diagnostic testers from Bosch. In addition, more and more of the previously purely mechanical interventions on vehicles now require the use of electronic control units.
On-board diagnostics using a PC
Until recently a diagnostic procedure, which required access to stored fault codes and other data was only possible with the use of dedicated equipment or relatively expensive code readers or scanners. However, with the proliferation of cars with EOBD/OBD-2 (European/On-Board Diagnostics, version 2) it is possible to extract information from ECUs using a simple interface lead and a standard computer running appropriate software.
Since 1 January 2001, all cars sold in Europe must have onboard diagnostic systems. European Directive 98/69/EC mandated that engine emissions must be monitored. The cars must also be fitted with a standard diagnostic socket
Equipment Available
The only equipment needed is a simple interface cable that connects the diagnostic socket to a serial port on the computer. This usually contains a custom[1]built circuit that uses surface-mount semiconductors that are designed for interfacing an automotive ECU to a PC. An extension lead can be used to allow connection to a PC that is bench mounted. A good design feature to look out for is that the earth or ground pins in the DLC plug are longer than the others.
A number of computer programs are available that will ‘translate’ the DLC signals into a readable format. One particularly good and reasonably priced program is ‘Vehicle Explorer’ created by Alex C. Pepper. As well as displaying DTCs this program allows monitoring of sensor signals in both numerical and graphical formats. Data can be recorded, during a road test for example, and then played back for analysis back in the workshop
Summary
Unfortunately, even though a common standard has been developed some manufacturers have interpreted it in different ways. However, it is now possible to access detailed information from many vehicle systems that until recently were only available to the main dealers.
Out of interest (and because I wanted one!) when I was writing this section, I bought an interface and cable for about £40/$60. Together with the software, I now have a powerful diagnostic tool – at a very reasonable price.
