Scan Tool Limitations and Use

SCAN TOOL LIMITATIONS AND USE
The "Scan tool" allows a quick check of sensors and switches which are inputs to the ECM. The "Scan tool" allows one to manipulate wiring harnesses or components under the hood while observing the "Scan Tool" readout. This helps in locating intermittents with the engine not running.

INTERMITTENT CONDITIONS
The "Scan tool" is helpful in cases of intermittent operation. The tool can be plugged in and observed while driving the vehicle under the condition where the light comes "ON" momentarily, or the engine driveability is poor momentarily. If the problem seems to be related to certain areas that can be checked on the "Scan tool", then those are the positions that should be checked while driving the vehicle. If there does not seem to be any correlation between the problem and any specific circuit, the "Scan 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 "Scan tool" is also a useful and quick way of comparing operating parameters of a poorly operating engine with a known good one. For example; A sensor may shift in value but not set a diagnostic trouble code. Comparing with a known good vehicle may uncover the problem.

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 technicians ability to understand the system he is trying to diagnose as well as an understanding of the "Scan tool's" limitations. Therefore, the technician should read the tool operating manual to become familiar with the tool. The following information will describe most of the "Scan tool" positions and how they can be helpful in diagnosis.