1. Autos

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Definition: A code number generated by a vehicle's onboard computer that corresponds to a specific fault. Most computerized engine control systems have a certain amount of self-diagnostic capability. When the engine is running and the computer detects a problem in one of its sensor or output circuits, or even within itself, it triggers a trouble code. In some systems, the code number is retained in memory. In others, the code is not stored but is regenerated when a mechanic runs the system through a special self-diagnostic test. The only indication of trouble is when the "Check Engine" light on the instrument panel lights up. What does it mean? It depends on the problem. Sometimes it's nothing serious, but it could signal a failure that might lead to further problems. To understand trouble codes, you have to have a reference manual that tells what the numbers mean and explains the step-by-step diagnostic procedure for isolating the fault. Codes are read out of the computer by grounding the computer's diagnostic connector or by using a scan tool to access the computer system. (See also Diagnostic Trouble Codes).

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