Oxygen (O2S) Sensor
WARNING: This page is about a different car, the 1994 Mazda Protege, 1994 Mazda MX-3, and 1994 Mazda 323. However, it is still accessible from the selected car via links, so may be relevant.
- Warm engine to operating temperature. Operate engine at idle. Disconnect O2S sensor electrical connector. Connect voltmeter between connector and ground. On MX-3 DOHC, increase engine speed to 4500 RPM until voltmeter indicates about .7 volt. On MX-3 SOHC, Protege, and 323, increase engine speed to 3000 RPM until voltmeter indicates about .55 volt.
- Observe voltmeter while rapidly accelerating and decelerating engine speed. Voltage should be 0.5-1.0 volt during acceleration and 0.0-0.4 volt during deceleration. Replace O2S sensor as necessary.