Typically modern automotive systems have a seperate sender for the temp gauge, which is a pretty rough signal meant to give an approximate visual representation of whatnthe cooling system is doing. The ECM/PCM have a sender of their own that is typically quite fine, allowing the module to read in tenths of degrees for fine fuel system changes and things like enabling cooling fan modules and so on. Typically gauge senders are single wire, utilizing a block ground for its signal while a PCM sender will have 2 or 3 wires, varying a voltage reading instead of a ground.
A decent scanner should help troubleshoot if this sender is malfunctioning or not. Just look for a live signal option and find coolant temp. Compare it to the gauge, best to do it with the engine cold so you can see a large differential if the sender is malfunctioning.