CAUTION: DO NOT attempt to measure O2 sensor output voltage with a conventional voltmeter. Current drain of voltmeter could damage sensor. O2 sensor voltage signal can be measured using a 10-megohm (minimum input impedance) digital voltmeter. For further information, see appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section.

Start engine, and warm to operating temperature. Ensure vehicle is operating in closed loop. Unplug O2 sensor connector at sensor.
Using Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, connect DVOM (on voltmeter scale) between ground and O2 sensor connector (sensor side).
Place a short jumper wire in sensor lead (computer side). While holding jumper wire in one hand, alternately touch negative battery terminal and then positive terminal with other hand. DO NOT touch sensor lead directly to battery.
Monitor DVOM reading. When negative battery terminal is touched, O2 sensor output voltage should increase (up to one volt). When positive battery terminal is touched, O2 sensor output voltage should drop (as low as .1 volt). If O2 sensor does not respond as indicated, replace sensor.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Oxygen (O2) Sensor

Use the Manual With the Right Hardware

When to See a Mechanic

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