Think you have to wait for a luxury car to have an onboard computer? Think again. Most vehicles today use an onboard computer to monitor and manage several of your vehicle's operating systems. These on-board computers have more memory capacity than the first spacecraft that went to the moon. 

If this computer detects irregularities in your vehicle's operating systems, it will often turn on a dashboard alert light. Using a specialized scanner, a technician can read a trouble code off the computer that details what went wrong.

After 1996, most trouble codes were standardised across manufacturers. So now all vehicles use five character codes to report problems. The computer can even remember problems that have flared up and then returned to normal. Dashboard alert lights come on if something substantial has occurred. More serious problems are detected and stored for analysis by a technician. Early detection of these problems can reduce repair costs and prevent breakdowns.