Since model year 2003, a growing number of domestic and import vehicles have been built with a new onboard communications protocol called CAN (Controller Area Network). CAN is essentially an engineering standard for how computers and modules talk to one another via the serial data bus in a vehicle's wiring system. It's a high-speed standard designed for powertrain control modules, antilock brakes and stability control systems.

The CAN protocol was created back in 1984 by Robert Bosch Corp. in anticipation of future advances in onboard electronics. The first production application was in 1992 on several Mercedes-Benz models, but CAN is now being used on more and more new vehicles. By 2008, all new vehicles sold in the U.S. will be required to have a CAN-compliant onboard diagnostic system. But you won't have to wait until then to encounter CAN diagnostics because many of the early applications are already out of warranty and may be coming into your shop now.

Geek-Speak
If you're not up to speed on the latest electronics and don't know a data bus from a school bus, diagnosing CAN systems will be a challenge. Even so, you don't have to be an engineer to perform basic diagnostics on CAN-equipped vehicles because the problem-solving is essentially the same as current OBD II vehicles. The only difference is that you need a CAN-compliant scan tool to read the vehicle serial data. Most current generation scan tools don't ...