How to Test an Aurora O2 Sensor

The heated oxygen sensor in the Oldsmobile Aurora receives a signal of 450mV from the powertrain control module, or PCM. Once the oxygen sensor reaches 600 degrees Fahrenheit or over, it goes into closed loop -- which means that it is working. It generates a voltage that is dependent on the amount of oxygen in the exhaust. Once in closed loop, the oxygen sensor sends a rich or lean signal, if applicable, to the PCM. If the amount of oxygen in the exhaust is high, the engine is running rich -- too much gas in the mixture, and the voltage will go above 450 mV. In a lean condition, there is too much air in the mixture, the system is lean, and the oxygen sensor voltage will be below 450 mV. The computer turns the engine light on when it receives a signal with the incorrect voltage.

Things You'll Need

• Power graphing meter

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Instructions

1. • 1

     Allow the vehicle to come to operating temperature. Connect the power graphing meter's red test lead to the to the signal wire -- this is the purple or purple with white stripe wire.

   • 2

     Connect the blue test lead to the same wire. Connect the black test lead to a known good ground. A known good ground is the battery negative terminal or any bare metal that is not aluminum or chrome.

   • 3

     Instruct a helper to hold the rpm at 2,500. Watch the power graphing meter. You should see two lines on one graph -- one for each signal. The numbers will go up and down -- hitting a maximum and a minimum. The maximum number should always be over 800mV, while the minimum number should be below 250 mV.