Heated Oxygen Sensor (Ho2S): 2.5L
WARNING: This page is about a different car, the 1995 Mazda Millenia. However, it is still accessible from the selected car via links, so may be relevant.
- Warm engine to normal operating temperature. Disconnect oxygen sensor connector. Connect negative voltmeter lead to ground. With engine running at idle, voltage at terminal "A" should be fluctuating at less than one volt. See Fig 1 . While accelerating engine, voltage should be .5-1.0 volt. While decelerating engine, voltage should be .1-.4 volt.
- To test oxygen sensor heating element, let sensor cool to room temperature. Disconnect HO2S connector. On front (3-pin) oxygen sensors, measure resistance across terminals "B" and "C". See Fig 1 . On rear (4-pin) oxygen sensors, measure resistance between terminals "C" and "D". Replace sensor if resistance is not about 6 ohms at 68°F (20° C).