Sorry, the NHTSA has not posted this TSB document yet.
You can still get the detailed info from Chevrolet for this TSB. Call your local Chevrolet dealer's service department & ask for a copy of TSB# PIE0349.
Engineering Information – Service 4WD Message Displayed and DTC C0398
Condition
Important: If the customer did not bring their vehicle in for this concern, DO NOT proceed with this EI.
Some customers may comment on a “Service 4WD” message displayed.
During diagnosis a technician may find DTC C0398 (Range Actuator Position – Range Position Correlation).
Cause
GM Engineering is attempting to determine the root cause of the above condition. Engineering has a need to gather information on vehicles PRIOR to repair that may exhibit this condition. As a result, this information will be used to "root cause" the customer's concern and develop/validate a field fix.