Limitations, Uses & Positions

The SCAN tool allows a quick check of switches and sensors that input to the ECM. The data only updates every 1.25 seconds, which makes the tool less effective than a voltmeter for detecting an intermittent that lasts less than 1.25 seconds. However, the SCAN tool allows for manipulation of wiring harnesses or components under the hood while observing the SCAN readout. This assists in locating intermittents with the engine off.
The SCAN tool is also a useful and quick way of comparing operating parameters of a poorly operating engine with a known good one.
The SCAN tool has the ability to save time in diagnosis and prevent the replacement of good parts. The key to using the SCAN tool successfully for diagnosis lies in the operator's ability to understand the system being diagnosed and the limitations of the SCAN tool.