''

Troubleshooting

In general, troubleshooting is the identification of, or diagnosis of "trouble" in a system caused by a failure of some kind. The problem is initially described as symptoms of malfunction, and troubleshooting is the process of determining the causes of these symptoms.

A system can be described in terms of its expected, desired or intended behavior (usually, for artificial systems, its purpose). Events or inputs to the system are expected to generate specific results or outputs. (For example selecting the "print" option from various computer applications is intended to result in a hardcopy emerging from some specific device). Any unexpected or undesirable behavior is a symptom. Troubleshooting is the process of isolating the specific cause or causes of the symptom. Frequently the symptom is a failure of the product or process to produce any results. (Nothing was printed, for example).

The methods of forensic engineering are especially useful in tracing problems in products or processes, and a wide range of analytical techniques are available to determine the cause or causes of specific failures. Corrective action can then be taken to prevent further failures of a similar kind. Preventative action is possible using FMEA and FTA before full scale production, and these methods can also be used for failure analysis.

Aspects

Most discussion of troubleshooting, and especially training in formal troubleshooting procedures, tends to be domain specific, even though the basic principles are universally applicable.

Usually troubleshooting is applied to something that has suddenly stopped working, since its previously working state forms the expectations about its continued behavior. So the initial focus is often on recent changes to the system or to the environment in which it exists. (For example a printer that "was working when it was plugged in over there"). However, there is a well known principle that correlation does not imply causality. (For example the failure of a device shortly after it's been plugged into a different outlet doesn't necessarily mean that the events were related. The failure could have been a matter of coincidence.) Therefore troubleshooting demands critical thinking rather than magical thinking.

It's useful to consider the common experiences we have with light bulbs. Light bulbs "burn out" more or less at random; eventually the repeated heating and cooling of its filament, and fluctuations in the power supplied to it cause the filament to crack or vaporize. The same principle applies to most other electronic devices and similar principles apply to mechanical devices. Some failures are part of the normal wear-and-tear of components in a system.

A basic principle in troubleshooting is to start from the simplest and most probable possible problems first. This is illustrated by the old saying "When you see hoof prints, look for horses, not zebras", or to use another maxim, use the KISS principle. This principle results in the common complaint about help desks or manuals, that they sometimes first ask: "Is it plugged in and does that receptacle have power?", but this should not be taken as an affront, rather it should serve as a reminder or conditioning to always check the simple things first before calling for help.