Diagnostic trouble code generation, diagnostic trouble code/fault status
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Diagnostic trouble code generation, diagnostic trouble code/fault status
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In the event of a malfunction, when the transmission control module decides that a fault exists, a diagnostic trouble code will be stored. Faults can be assigned a status, as follows: - the fault is present right now (P) - the fault has occurred but is not present right now (I) The transmission control module's decision process is a continuously ongoing computational routine which specifies both the appropriate diagnostic trouble code and the current status of the fault. Let us assume, for example, that shifting solenoid S1 is permanently shorted to ground (pin 1 of the transmission control module is incorrectly grounded). According to the diagnostic trouble code table, the appropriate trouble code is P1852. During the drive cycle in which the fault occurs, the transmission control module stores both fault status P and diagnostic trouble code P1852. When the car is subsequently stopped, the ignition switch turned to the ON position and later to ON and START, the transmission control module's fault handling subroutine starts running again. If at that time the car is stationary, shifting solenoid S1 should not be active and the transmission control module will decide that the fault is not present, that is to say it stores fault status I and diagnostic trouble code P1852. When the car is driven off, the fault handling subroutine continues running and after a period when all fault criteria have been satisfied, the transmission control module again decides that the fault is present and its fault status is changed to P. The period during which the status of a fault is determined depends on the drive cycle (engine load and rpm) and type of fault, and may vary from a few seconds to 10 minutes.
