http://www.businessweek.com/stories/2006-04-23/why-your-car-goes-crazy

Lifestyle

Why Your Car Goes Crazy


These days more and more owners are complaining about a myriad of intermittent problems with their vehicles, and they range all over the spectrum. Sudden window openings, power-seat movements, engine shutdowns, navigation system anomalies, transmission-shifting glitches, remote-locking system failures, windshield wipers coming on, alarms engaging and countless other operating deficiencies are reported around the country. Shop technicians seem unable to fix or even duplicate such symptoms when the vehicles are brought in for repairs.

So why is this happening? Well, according to John Hall, the main reason is that over the past 20 years the role of electronics in vehicles has moved from being "one of the band members" to being "the conductor." Hall is a expert in automotive electronics and has written a book called, Semiconductor Design and Implementation Issues In Integrated Vehicle Electronics.

In his book Hall explains how electronics, specifically microprocessors, now run your entire vehicle. Microprocessors are everywhere in our lives. There's at least one in your microwave oven, TV, VCR, DVD -- and a whole bunch of them in your car.

That's where the problem begins. The manufacturers have constantly strived to develop capabilities that large and varied populations will embrace and -- more important, pay for. They have known for decades that fewer and fewer buyers will read complicated instructions for operating all the gadgetry, so the entire thrust of development is toward automated, "idiot-proof" features -- and lots of them.

OUT OF TUNE. The answer to the manufacturers' dilemma is the microprocessor. More to the point, it's the control module. This is the central brain built into the vehicle, and its job is to consolidate and control a variety of functions. In actuality the control module (called many different names by individual manufacturers) is a bundle of chips all integrated into a central command unit. Individual devices that run, for instance, the windshield wipers or a four-wheel-drive transfer case, all talk to the control module, which allows the vehicle's electronics to handle many tasks at the same time.

Why do this, you might ask? Well, if you wanted to control each of a modern vehicle's electrical components individually any other way you'd have to hard-wire controls to every one of them and use a lot of switches. That would mean miles of wire and piles of other components for which there's simply no room, not to mention weight and cost concerns.

The microprocessor-packed control module is the solution to the manufacturers' problem. It becomes the conductor of the vehicle's electronic orchestra. Unfortunately, the solution to the problem creates new opportunities for failure. One of these is the wiring that goes from the electronic devices to the control module.

THE ARMY WAY. Wire is a great transmitter of electrical current, of course, but it is also susceptible to high-voltage spikes from static discharges (lightning, high-voltage sources, shortwave radio, etc.) and can act like an antenna if not properly shielded.

Another failure mode happens when the control module's microprocessors become overloaded with errant (false) signals from any of the controllers or sensors that are connected to it. These devices are just as susceptible to outside electrical noise as the microprocessor itself and it's nearly impossible to engineer around every potential failure or error in a cost-effective way. Military equipment is incredibly expensive because it is protected from such interference, but no one could afford an automobile with the same level of sophistication.

The reason your car might do weird things -- or do nothing at all -- is essentially the same reason your computer might freeze. Lousy software design aside, computers and cars largely use complementary-symmetry metal oxide semiconductors (CMOS) and similar devices. Any voltage surge (we're talking about very, very small voltages here) causes CMOS circuits to stop functioning until power is removed and reapplied. Once the frozen CMOS circuits are turned off and back on, they work fine and show no evidence anything ever failed.

SHOCKING RESULTS. There are protection techniques currently in use by manufacturers to limit stray signals to electronic circuits. Resistors and diodes are added to circuits to filter incoming high voltage signals and the Control Modules themselves are packaged in interference-shielding materials. However, vehicles have lots of wiring -- and any single wire on any day can suddenly become an antenna that is tuned precisely to some stray electromagnetic signal.

Under the right circumstances a policeman's radio, CB, microwave tower, or even a passenger sliding over the seat can generate a high static voltage spike that results in a momentary, erratic, and false signal to the vehicle's control module. This can result in one of innumerable things happening to the vehicle. (By the way, that spark you get when you touch a switch plate on a winter's day has between 2000-3000 volts -- more than enough to throw off you car's electronics!)

The problem is that many of these symptoms can't be traced by even the most competent technicians at the shop level, thereby leading owners to conclude that they have a lemon. In addition, many problems can occur after sound systems or other aftermarket electronics have been installed in vehicles because the integrity of the wiring has been compromised. That's why dealerships are telling customers not to install aftermarket devices that haven't been certified by vehicle manufacturers. Eventually the state of the art in electronic design will catch up with, and solve, the potential for false-signal failures in vehicles.

PROCEED WITH CAUTION. Until then the best protection for consumers is to avoid cutting-edge technology features in new vehicles. Currently, these would include active suspension, I-Drive-type systems, and keyless ignitions.

Basically, anything that is going to cost a lot of money to fix outside of warranty should be strongly considered before buying. Such gadgetry can disable the vehicle when it fails. Wait a few years for these devices to get the bugs ironed out, and for them to become reliable, mainstream features.


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