oxygen sensor

[Clint F.]

The signs vary depending on the year and model of your car.  A non obd-2 
generally won't set a check engine light for a bad O2 unless it is totally 
screwed up.  I usually notice a bad one (when not directly testing one) by a 
car that runs fine, other than an occasional mild hesitation on 
acceleration, a noticeable exhaust smell, and the key- a very slight, mild 
surging sensation when cruising at freeway speeds.
These indicate a sensor that is "lazy", or slow to respond to the O2 content 
of your exhaust.  I've never ohm tested one.  If your resistance is off, it 
can go either way out of range. I generally use an osilliscope to watch the 
voltage waveform.  A good digital meter will work too. Set it to volts, 
ground the black lead, and hook the red one to the O2 signal wire (at 
connector with boot pulled  back, or with a wire piercing probe) The voltage 
should steadily swing from .2 to .8 volts and back around once a second. At 
2500 rpm, 10 times. (this is hard to see on most meters)
Some common things that cause O2 sensors to go bad are age, using non-sensor 
safe gasket maker(silicon contaminates the material) coolant 
contamination(bad head gasket) and severe flooding(filling the exhaust with 
raw fuel, don't worry, if your car is doing this, it probably isn't running)

>From: Trevor Irwin <trirwin at indiana.edu>
>To: quattro at audifans.com
>Subject: oxygen sensor
>Date: Thu, 7 Jun 2001 20:23:13 -0500 (EST)
>
>
>What are the symptons of a bad oxygen sensor? Also, when you check the
>resistance on a bad one (as per the Benteley), is there usually more
>resistance or less? (Benteley indicates should get 3-15 ohms). Thanks for
>any insight.
>
>-------------------------------
>T. L. Irwin
>T104 Coordinator
>Swain East 335
>855-3573
>php.indiana.edu/~trirwin
>

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