Страница 1 мировой engineering стандарты общая спецификация

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GM WORLDWIDE ENGINEERING STANDARDS
GMW3110
E1.1 DTC Status Byte Bit Operation. 
The following figures illustrate the expected values of the status byte for
various types of DTCs under various operating conditions. In general, DTCs may be divided into two major
categories, Powertrain and Non-Powertrain DTCs.
For Non-Powertrain DTCs, the DTCs may be categorized based upon how the DTC is latched. Latching a DTC
refers to retaining the present state of the current bit in the status byte. This retention may be permanent or of
limited duration until an event occurs (e.g., ECU power up reset).
Latching a DTC alters the operation of the ECU with respect to the execution of and/or reaction to the results
of a supported diagnostic test. A diagnostic test consists of actions performed from a given moment when all
conditions to start a diagnostic fault detection algorithm are fulfilled until the moment a diagnostic fault
detection algorithm makes a pass/fail decision. A failed diagnostic test indicates that the detected failure is
severe enough to set a DTC with current status.
Certain diagnostic tests are only run once per ignition cycle (e.g., EEPROM checksum test where the
checksum is calculated at power down and recalculated at power up with a mismatch indicating a fault). Once
the Current status is set to true, it remains set to true for the duration of the ignition cycle because the
diagnostic test does not run until the next ignition cycle. This is not considered a latching DTC.
All Non-Powertrain DTCs may be classified as belonging to one of three types:
•
Non-Latching DTCs (Figures E1 and E2): 
(Also called Condition Latching DTCs) Once the Current
status has been set to “True”, it remains set to true until the diagnostic test makes a pass decision. Most
currently implemented DTCs are of the non-latching type.
•