WARNING: This page is about a different car, the 2005 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: HO2S (Front) Signal - Oscilloscope Graph
Courtesy of MAZDA MOTORS CORP.
PCM terminal: 4W(+) <--> 4A(-)
Oscilloscope setting: 0.2 V/DIV (Y), 2.0 ms/DIV (X), DC range