If a car is running the O2 sensor will vary in voltage. For example the Heated O2 sensor on my 93 2.0L goes between 0 to 1 volt while the car is running depending on the O2 output in the exhaust. Now when you initally turn the car on 5 volts go from the O2 relay to the senor to heat up the element in the sensor. To check a sensor you need to turn the car off and check the OHM reading of the sensor. Unplug the sensor from the connector. Check on the net for the specs as to what your sensor should be reading. I recommed that you take two readings. One while the car is cold and hasn't been run yet and the next one after the engine warms up. check to see if the OHM reading is the same in both conditions. I am not sure how the V6 is setup Exhaust wise but there could be up to three O2 sensors. One for each side of the exhaust and one should be after the CAT somewhere. this allows the ECU to adjust the fuel trims. SAFETY NOTE: DO NOT CHECK OHM READINGS WITH IGNITION SWITCH ON! It will damage the Ohm meter and could casue a shock to you as well. Hope this helps. Good Luck

 

When did you install the intake? was it recently? Reset the battery and see if the light comes back on first.

And SANG I was thinking the Cat as well because on sensor is proir to the cats and the other is after. but Deff try the sensors first and work from there.... And reset the battery and make sure it comes back on, also for kicks and giggles make sure the gas cap is on tight cause that can trip a code but it is usually differnt I think Pressure or fuel pressure somehting like that. Just suggestions

 

CAI was installed awhile ago, so I don't think it's that. I'll test the sensors tomorrow at work.

 

If the gas cap isn't tight you'll get a vac code nothing even near the O2 sensor code. I figure the O2 sensor would be easier to test vice trying to tell if there's a cat problem. If the O2 sensors are reading fine and resistance is in spec then the only thing it CAN be is the caty.

 

I hope not, $115 for a sensor isn't my idea of fun spending. It only cost me $11 to replace an O2 sensor on my old '94 Dodge. I guess all I can hope for is that only one of them is bad. Would still be cheaper than replacing the Cat though.

 

Exactly the reason I said to check the O2's first easier to check cheaper to replace....

 

It may actually be worth it in this case to take the car to a mechanic or the dealership. You can get a code read for free at autozone/advance (oh yeah, all cars after 1996 use ODBII computers) but what they use is a simple reader which is basic at best. Most mechanics and all dealerships will have a scan tool that goes much more indepth than a reader will. I am having a similar problem with my 97 Eclipse RS and the reader at autozone didn't help a bit.

 

A reader is a reader. It's gonna give the mechanic the same thing it gives Auto Zone. The only difference is the Snap On Scanner II will tell them what the code means instead of having to look it up online or in a book. There's NO difference in what it will tell though. The difference is that the mechanic will tell you right there the same things we'll tell you here AND he'll charge you to tell you it.

 

So if I use a multi-tester. How would I go about testing the sensor? What would be the best setting on my tester to test with?

 

well if it is the cat then time to get an upgrade...