What does the yellow LED indicator mean on the Code Reader?

A yellow LED indicates one of two conditions: either a 'Pending' Diagnostic Trouble Code is present, or some of the vehicle's emission monitors have not yet run their diagnostic self-testing. A pending code is confirmed by a numeric code and the word 'PENDING' on the LCD display, while unrun monitors are shown as flashing Monitor icons on the display. Whether the vehicle can pass an emissions test under a yellow LED depends on local regulations. (Page 19)