Quote:
falconjoe - 7/26/2004 4:05 PM
Thanks MTI (yet again) How does one "check" the O2 sensor? Does one need a special tool?
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How do I test my sensor?
Using a digital voltmeter with reasonably high impedence (20K ohms or so), you can measure the voltage output of your O2 sensor while it's connected to the computer, with the car warm and running of course. Just find the single wire connector coming from the sensor that goes to the computer - not the one that has two wires, that's the preheater on some sensors. Set your meter to a range near 1 volt - the sensor's output falls in the 0-1 volt range. Ground the (-) probe to the head or the battery, and clip the (+) lead to the sensor output. You should be getting a reading in the neighborhood of 0.45 volts, fluctuating a bit up and down. If you get no voltage or a low voltage, your sensor needs replacement.
The life of an O2 sensor varies depending on fouling, vibration, but Mercedes estimated it to be somewhere under 100K miles. As a result, they built in a signal light that got tripped by the odometer at approximately 60-90K miles that set off a dash light. In early model W201s, the "reset" of the dash light was accomplished by removing the bulb from the socket. Later, around 1987, they changed it so that you could reset the light via a button located under the passenger seat carpet near where the cable from the sensor enters the cabin. If it is the sensor, remember that the Bosch sensor for a V-8 5.0L Mustang is the same part with a different wire harness, but a lot cheaper!