What is a Diagnostic Scan Tool?

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  • Written By: Troy Holmes
  • Edited By: W. Everett
  • Last Modified Date: 27 September 2019
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Most modern automobiles today are full of technology and gadgets. This technology provides both comfort and efficiency in the motor and cabin of a car. Because of this advance technology, a diagnostic scan tool is required for troubleshooting issues in modern automobiles. This tool connects to the computer processor port in the vehicle and reports any abnormalities with special error codes.

An on-board diagnostic information system (OBD-II) is the standard computer system in most automobiles today. This system was built in an effort to help car manufacturers maintain fuel emissions standards. The OBD-II system requires a special diagnostic scan tool to read the computer error codes. This system typically manages fuel economy, car timing, and performance characteristics.

Today’s automobiles typically have a special check engine light on the instrument panel. This light illuminates when the car diagnostic system recognizes a failure condition. There are many possible causes that may trip a check engine light. The diagnostic scan tool is used by mechanics to determine what specific system error is causing the failure. Without this tool, diagnoses would be extremely difficult.

Older cars were primarily built with mechanical devices with limited diagnostic automation. This required a mechanic to have trouble shooting skills that were more of an art then a science. Today’s mechanics are dependent on the diagnostic scan tool to determine the mechanical problems of the vehicle.


The initial versions of the scan tool were extremely expensive. This made car repair virtually impossible for a home mechanic. Within the last decade, the diagnostic scan tool has become more affordable. Today it is available in a small battery-powered unit and can be easily connected to the car OBD-II port.

The scan tool returns special codes that are based on dealer computer specifications. These codes must be matched to a dealer repair manual to determine the fault condition. Most automobile repair manuals can be purchased directly from the dealer. This manual is a full how-to manual on how to fix the specific error conditions within the car.

Once a car has been fixed by a mechanic, the OBD-II system must be reset. This reset option is typically performed with the diagnostic scan tool. Failure to reset the system will give the driver false error code readings. This is typically represented by a blinking check engine light after leaving the repair shop. The only other method of resetting this error condition is to disconnect the battery for several minutes.


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