General Specification Electrical Function gmw3110 General Motors Local Area Network Enhanced Diagnostic Test Mode Specification

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. 

Limited Duration Latching DTCs (Figures E3 and E4):
Once the Current status has been set to true, it 
remains set to “True” regardless of the results of the diagnostic test until a specified event (e.g., power up 
reset) occurs.
Note:
The DTC is cleared when a clear diagnostic information command is received. Since the DTC is 
latched, the diagnostic algorithm does not run. Therefore, the repair cannot be verified unless the specified 
event occurs (e.g., ignition is cycled). 

Permanently Latched DTCs (Figures E5 and E6): 
Once the Current status has been set to true, it 
remains set to true regardless of the results of the diagnostic test. This type of DTC cannot be permanently 
cleared and requires ECU replacement. The DTC can be temporarily cleared using a scan tool, but the 
DTC returns at the next power up of the ECU. 
Powertrain DTCs are also categorized into three main categories; Type A, Type B, and Type C (there is a 
fourth category for DTC not supported that is not illustrated here, as these DTCs are in the ECU software but 
are not run) based upon illumination of the Malfunction Indicator Lamp (MIL).
Note:
Due to varying regional requirements, the following tables cannot illustrate all possible cases. These 
tables are provided as examples and, in case of a conflict, do not supersede any documented diagnostic 
requirements. 

Type A DTCs (Figures E7, E8, and E9): 
The ECU sets the status current, history, and requests 
illumination of the malfunction indicator lamp (MIL) when the diagnostic runs and fails. The current status 
is cleared when a Test Pass is reported but the MIL remains illuminated for 3 consecutive ignition cycles, 
depending on the DTC, when the diagnostic runs and does not fail. 
