Welcome to Allpar. You may still have a fault code stored in the TCCM (Transfer Case Control Module). The SERVICE 4WD light can be considered a warning light for a malfunction.
A more advanced scan tool is required for accessing modules other than the PCM, so this may require a dealer's StarScan/StarMobile/WiTech tool.
If you are still under the 3/36 warranty then let the dealer handle it. Your owners manual may also mention to take it to your dealer for this light. Please post back with what they found as I am interested in what happened.