Some troubles are immediately detected by the ECU with the key in the run position and without the engine running. Other
troubles are not detected until very specific test conditions are met such as engine coolant temperature within a range,
speed within a range for a duration of time, throttle percentage within a range, etc.
If the trouble codes are erased when the trouble remains unresolved, the trouble code will reappear in the ECU the next
time the ECU performs the specific diagnostic test for that trouble.
If the trouble is resolved but there is a stored trouble code, sometimes the ECU will detect the resolution and clear the
trouble code or more likely, classify it as “historical” trouble.
If the trouble is resolved and the user clears the trouble codes, the trouble history will be cleared.
If the user intends to have another colleague or mechanic investigate the problem, it is not recommended for the user to
clear the trouble code since doing so may erase information helpful to others who may investigate the issue.
Real-time information about various sensors is called “Live Data”. Live Data includes parameter identifications (PIDs) of
the running engine such as oil pressure, temperature, engine speed, fuel oil temperature, coolant temperature, intake air
temperature, etc. Based on these parameters, we can predict directly where the problem lies, which helps to narrow the
scope of maintenance. For some vehicles, during their actual operation, the problems such as performance characteristics
or sensitivity reduction, can be evaluated using live data.
Click the magnifying glass on the top right, you can search for related PIDs based on keywords
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