Diagnostic Aids

Use the DTC Descriptor list above to determine the module which is not communicating.
If there are multiple non-communicating modules choose the one closest to the data link connector (DLC).
Use Data Link References to determine if the module uses high or low speed GMLAN serial data communications
Some modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no module output voltage circuit is shorted to ground before replacing the module.
This diagnostic can be used for any module that should communicate with high or low speed GMLAN serial data providing the vehicle is equipped with the option that uses that module.