This paper discusses both basic and advanced diagnostic features of gas ultrasonic meters (USM), and how capabilities built into todays electronics can identify problems that often may not have been identified in the past. It primarily discusses fiscal quality, multi-path USMs and does not cover issues that may be different with non-fiscal meters as they are often single path designs. Although USMs basically work the same, the diagnostics for each manufacturer does vary. All brands provide basic features as discussed in AGA 9 Ref 1. However, some provide more advanced features that can be used to help identify issues such as blocked flow conditioners and gas compositional errors. This paper is based upon the Westinghouse configuration (also knows as a chordal design) and the information presented here may or may not be applicable to other manufacturers.