- Diagnosing Intermittents

SCAN TOOL USE WITH INTERMITTENTS
In some scan tool applications, the data update rate makes the tool less effective than a digital multimeter - such as when trying to detect an intermittent malfunction which lasts a very short time. However, the Tech 1 scan tool does allow manipulation of wiring harnesses under the hood (engine not running) while observing readouts.

The Tech 1 scan tool or scan tool can also be plugged in and observed while driving the vehicle under the condition when the Malfunction Indicator Lamp (MIL) comes on momentarily or when engine driveability is momentarily poor. If the malfunction seems to be related to certain parameters that can be checked on the Tech 1 scan tool, they should be checked while driving the vehicle. If there does not seem to be any correlation between the malfunction and any specific circuit, the Tech 1 tool can be checked on each position, watching for a period of time to see if there is any change in the readings that indicates intermittent operation.

The Tech 1 scan tool is also an easy way to compare the operating parameters of a poorly operating engine with those of a known good one. For example, a sensor may shift in value but not set a Diagnostic Trouble Code (DTC). Comparing the sensor's readings with those of a known good one may uncover the malfunction.

A scan tool has the ability to save time in diagnosis and prevent the replacement of good parts. The key to using a scan tool successfully in diagnosis lies in the technician's ability to understand the system he is trying to diagnose as well as an understanding of the scan tool's operation and limitations. The technician should read the scan tool manufacturer's operating manual to become familiar with its operation.