Hello grees ; There is no adjustment on an O2/Lamda sensor. The computer sets a trouble code when it 'sees' something out of the ordinary on the fuel mixture circuit . Could be a weak O2 sensor, bad wire connection, vacuum leak etc. Assuming you do not have a drivability problem, ie. the car has not been acting/driving unusual before the light came on, try disconnecting the negative battery cable for 15 minutes to clear the code, and see if it resets when started. Check the connections while you wait. If it does not reset a code you are good to go. If it does it is probably new O2 sensor time.
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'94 940 150k, '86 240 170k, '72 142 KIA, '70 144 KIA, '69 144 RIP