Originally Posted by DONKY4444
It is a 2002 SSEi with 61K on it. I have never changed the O2 sensor before. I am currently getting around 21 MPG on the highway with a some what heavy foot. Before this started I was getting about 20 MPG.
Those mpg numbers are low for highway, your fuel economy is not good. When the PCM detects an excessively rich condition, it will set DTC P0172. Follow the instructions BillBoost laid out & check those items that he called out. With 61k, it may not be a bad idea to replace the O2 sensor, plugs & wires for general measure.