Oxygen Sensor (O2S)

1997 Saturn SC1 AutomaticSECTION Oxygen Sensor (O2S)
  1. Start engine and warm to operating temperature. Disconnect oxygen sensor. Connect a DVOM between lead of oxygen sensor and ground. Place DVOM on the 2-volt scale. Voltmeter reading should increase to greater than .8 volt.
  2. Using another DVOM on the 20-volt scale, connect voltmeter in series between the oxygen sensor wire from PCM and positive post of battery. Reading on voltmeter connected to oxygen sensor should decrease to a low voltage (less than .3 volt).
  3. If a second DVOM is not available, install short jumper in oxygen sensor wire from PCM. Hold jumper in one hand and touch positive post of battery with other hand. This should cause oxygen sensor to produce less than .3 volt. For additional testing procedures, see the TESTS W/CODES article.
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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.