try to reset it. the main reason for close and open loop is to get the engine warmed up, along with all of the sensors. they go in closed loop b/c some of the sensors (like the o2) can't read anything below a certain temp. unplug the battery, and let it sit for a while, or turn the screw on your ecu, and that should do the trick. why do you ask anyways?
Well when my O2 sensor went bad it triggered the check engine light. SO i went to the stealer and they said it was the O2 and they quoted me $150 to do it, which wasn't covered under my 72K Emissions/Drivetarin warranty then. So I basically said to piss off till i had the cash to buy one. In return they said they would keep it in a continous closed loop to stop the light from coming on (that light is a whole other story). Well I went back got the sensor changed but looking over the workorder it lists nothing about reseting it and nobody seems to remember if in fact they did reset it. In the end it only cost $64, somehow someway I had a warranty that paid for half or something like that.
well, the 02 sensor is only about that much, and takes 5 miniutes to put in (with the special $5 socket). I have one, and works like a charm. it is a normal socket w/ a slit cut out of it to go around the wires. the engine will come out closed loop when it warms up, or the mil is turned off (by reseting the computer)