1995 volvo o2 sensor..which wire???

The 2010 Dodge Caliber O2 sensor wiring has four wires: two white, one gray, and one black. The wires are typically color-coded, so you should be able to match them up with the wires on the replacement O2 sensor.
Here is how the wires are typically connected:

• White wire: Sensor signal wire
• White wire with black stripe: Sensor signal ground wire
• Gray wire: Heater power supply
• Black wire: Heater ground

You can use a multimeter to confirm the correct wires if you're unsure.

https://www.justanswer.com/dodge/19w1p-dodge-wires-oxygen-sensor-signal.html

There should have been an instruction sheet in the box with the sensor. If not, you may have to go back to the store and ask for one.
Most sensor brands are different.

White are the heaters
Black the ground

Grey (signal) or output wire

Back probe the grey wire & ground your
meter lead or oscilloscope to chassis ----- NOT THE SENSOR GROUND

No voltage goes to the O2 --- it is an output sensor

The paperwork with the bosch o2 sensors should have a wiring diagram for splicing the wires.

Well - I'm not sure which one you mean - front or rear - here is a wiring diagram that should help you though.

Visit the on-line store, known as reliable-store, they have the repair manuals. I'm sure you will get the solution of your problem.
toyota celica

if memory is correct its the grey wire blacks ground whites are fore heaters

the white wires are the heater and the grey and black are the sensor wires the grey should be the one to the pcm