What can go wrong with your car’s electronics that control speed, braking and other things

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Electronic problems that can cause car troubles

A complex array of sensors, wires and computer chips now control just about every critical function in your car, including acceleration, braking, shifting gears and even the door locks. Toyota says it can’t find evidence that electronics are the root of its unintended acceleration problems, and it cites backup systems that would prevent trouble. But history shows that electronics are not immune from malfunction.

A look at glitches that can affect electronics:

ELECTROMAGNETIC INTERFERENCE — The air is full of electromagnetic signals from cell phones, wireless computers, radio stations and other sources. Under the hood, there are even more signals from wires, sensors, switches, coils and relays. All give off electromagnetic energy, and they can interfere with other devices given the right circumstances. Sometimes they can combine with each other to cause a glitch that is difficult to find or anticipate. Shorting wires or static electricity also can be part of the problem.

SOFTWARE MISTAKES — Car computers run on software specially designed to control acceleration, braking, steering and other critical tasks. But software engineers must write millions of lines of digital coding specific to each car, and mistakes can be made. Plus, the software writers can’t anticipate all possible circumstances that a car can encounter in the real world, as evidenced by the recent recall of 437,000 Toyota Prius and Lexus HS 250h gas-electric hybrids. Drivers can lose the “feel” in brake pedals while driving on bumpy roads due to a software glitch in the antilock braking system. A small software update cures the problem.

TIN WHISKERS — One insidious culprit in electronic failures is the “tin whisker,” a tiny splinter that sprouts without warning from the tin solder and finishes used deep inside electronics. They’ve short-circuited critical components of satellites, military weaponry and even forced nuclear power plants to shut down. Some experts worry the danger from whiskers is growing as governments eliminate lead from solder for health reasons. Lead prevents the whiskers from forming. With computer circuits getting smaller and closer together all the time, whiskers can bridge them and carry electrical charges to the wrong places, causing problems.

Henning Leidecker, chief engineer of the electronic parts office of NASA’s Goddard Space Flight Center in Greenbelt, Md., and an expert on tin whiskers, said in the last four years his office has been contacted by seven major suppliers of automotive electronics inquiring about failures in their products caused by tin whiskers.

He said his office has contacted Toyota offering to help analyze its acceleration problem, but hasn’t heard back.