Limitations

Scan tools have the ability to save time in diagnosis and prevent the replacement of good parts. The key to using a 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.

USE WITH DIAGNOSTIC CHARTS
Scan tools do not make the use of diagnostic charts unnecessary, nor can they indicate exactly where a problem is in a particular circuit. Diagnostic Trouble Code Charts incorporate diagnostic procedures using a scan tool where possible and most charts require the use of a scan tool when it is applicable.

INTERMITTENT CONDITIONS
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 can help in locating intermittents with the engine not running. The tool can also 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. These data values can be read and recorded for comparison with the average values for a normally operating system. Comparing actual data values with typical normal values for the same system can aid diagnosis.

Note: The parameters capable of being read vary with engine families. For a description of the data parameters used for diagnosis, see "Typical Scan Data Values". Typical Scan Tool Data Values
Only the parameters listed are used for diagnosis. If a scan tool reads other parameters, the values are not recommended by Honda for diagnostic use.