Computer: Roll down the window

Q: I just learned the windows, locks, mirrors and lights on my new car are all controlled by computers. Is this a good thing, should they ever break? I'm concerned the car will be difficult and expensive to repair. Did I have a choice, if I'd wished to go old-school on this stuff?

A: Your new car apparently uses a B-CAN, or body controller area network system to operate many of its features. With some earlier vehicles containing up to three miles of wire in heavy, complex wiring harnesses, this is a great way to simplify the electrical system and provide more reliable operation. Take your driver's-side door controls, for example. An old-school vehicle might have as many as 60 wires connecting the switches for the windows, mirrors, and door locks to their destinations in other doors. A B-CAN vehicle typically contains a processing module in the door, and communicates with other modules in the vehicle using signals carried on only one or two wires.

B-CAN systems improve reliability because low-current communication signals are much less troublesome than the much higher current needed in old systems.

Diagnosing a balky power window, mirror, light or lock controlled by a B-CAN system can be much easier.

A faster version of CAN (F-CAN) is also used to simplify and improve powertrain performance. As an example, instead of having individual vehicle speed sensors for engine, transmission and cruise control, the three control modules (if not combined) can share a single speed signal posted on the network.

A few old-school electrical systems may still be found on low-production or budget cars, but you'll be glad you made the choice you did. Getting rid of all that wire saves gas and reduces the price of the car. Fault diagnosis is now a professional's job, but should be needed much less often. Control modules are certain to be pricey, but aren't likely to break.

E-mail Brad Bergholdt at under-the-hood@juno.com