Heated Oxygen Sensor
WARNING: This page is about a different car, the 2003 Mazda Tribute, 2003 Mazda B4000, 2003 Mazda B3000, and 2003 Mazda B2300. However, it is still accessible from the selected car via links, so may be relevant.
Faults in Heated Oxygen Sensor (HO2S) or HO2S circuit should set a DTC. See QUICK TEST in appropriate SELF-DIAGNOSTICS article.