Practical use of diagnostics: Notes

There are several ways to decide if the malfunction is active right now or not as well as when the malfunction occurred: 

• Read off the diagnostic trouble code's counter, status identifier and frozen values.  By interpreting these you can find out when the malfunction was stored, how often the malfunction has occurred (intermittence) and what the driving conditions were when the malfunction was stored.
• Read off a parameter  for component/system and decide if the value is correct or not. By, e. g., manually affecting the sensor or the switch, you can decide immediately if the parameter (signal) with its circuit is correct.
• Trigger a component  (activate) and decide if the component/function is affected or not. By triggering, e. g., the relay and listening for its clicking sound or the function which is to be affected, it is possible to decide immediately if the component is correct.
• Decide if the vehicle shows any symptom (malfunction).  If the vehicle no longer shows the symptom, one may suspect that the malfunction no longer is active.

The following accounts in detail for some of the above.