WHAT TO DO WITH THE WIRES TO MAKE THIS WORK:
Your original O2 sensor has two wires of one colour (white). These wires are for the heating element. The third wire (black) transmits sensor data back to the computer. Get a UNIVERSAL 3-WIRE O2 SENSOR from your local auto supply store. (Bosch #13077 ??) Follow enclosed directions, cut off the old O2 sensor, and splice/solder/wrap the new unit onto the matching white and black wires.

If your car has a 3-wire sensor, then replace it with a universal 3-wire sensor. The heating element allows the O2 sensor to quickly reach operating temp (600 degrees). After starting the car, the engine computer will test the O2 sensor in 45-60 seconds. If you replace the 3-wire sensor with a 1-wire unit, the sensor will not warm up fast enough. The computer will then set the O2 sensor code and turn the Check Engine light on. If you reset the codes and restart the car, it will keep doing this over and over. (I learned this the hard way!)

COST: 1-wire universal replacement - $18
3-wire universal replacement - $45
3-wire OEM replacement - $120 (?)

The only hard part might be "untwisting" the wires if you try to do everything underneath the car. Simply pull the entire sensor and cable, noting where you unhooked it, splice/solder/wrap as needed, install the new sensor, then run the connector cable back up into the engine compartment. A wire coat hanger may come in handy to pull the wire back up!

[[ southern fried volvo '91 240 126k mi, with new O2 sensor! ]]