I remember I fought with my sim for almost 8 hours straight one day. There's 4 wires going to the O2 sensor: the ground, the accessory power, the heater power, and the signal return. After fooling with it, I ended up having to leave my o2 sensors on the pipe (drilled a hole for them, useless, but for storage), and leave the two heater wires going to the o2 sensor, rerouting the signal and ground to the sim. I double-tapped into the power wire, and cut the signal wire, routing the output from the sim straight to the ecu. Make sure you check voltages with a multimeter constantly, because we had issues getting the right connections.
This is how I finally had to end up wiring it:
That look similar to yours?