vandium7

Hi everyone.. I have an issue with my emissions and hopefully someone will have some advice. I own a 96 protege and I broke the downstream, 4 wire o2 sensor while changing my oil pan. After getting a price quote for $189 from autozone, I decided to buy a universal bosch from ebay for $20. Heres the problem.. the new sensor has three wires and the car harness has four.. now I'm convinced that since 3 of these wires are dedicated to heating elements and grounds, there must be a way to make this three wire work in place of the four wire that belongs there.. I certainly hope so considering the money I'll save.. Thanks in advance for your advice!
-vandium7