How to Test Auto O2 Sensors
- 1). Connect a voltmeter to the output wire of the oxygen sensor and the ground. The voltmeter should be set to "Millivolt."
- 2). Start the engine and run it for approximately 15 minutes to warm it up.
- 3). Observe the voltmeter. The needle should bounce around near the voltage that the voltmeter is centered at.
- 4). Have someone press the gas down and continue observing the voltmeter. The needle should go substantially lower than the centered voltage for a second, then spike back up past it before settling back down to idle voltage. If there is little difference in voltage, it is a sign that the O2 sensor might be bad.
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