Oxygen (O2) Sensor
- Disconnect 2-wire O2 sensor connector. Measure resistance between 2 White wires. Resistance should be about 4 ohms.
- Set voltmeter to 2-volt DC scale. Connect voltmeter leads between Black sensor wire and ground. Start engine. Voltmeter reading should vary from 0.1-0.9 volt as sensor temperature increases and air/fuel mixture changes. Replace O2 sensor if resistance is not as specified or sensor reaction time is too slow.