My car is constantly throwing DTC "522 - Rear O2 preheating" and "153 - Rear O2 sensor". I have cleared them 3x and they always return.
I read in following thread that front and rear HO2S are the exact same sensor for some Volvos.

http://www.brickboard.com/AWD/index.htm?id=1459996&show_all=1
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So I went to Bosch Auto Parts and used their vehicle part finder. They do not list a 1994 turbo 850, just 95 & 96. But the listed information leads me to believe the same is true for my car.

http://www.boschautoparts.com/VehiclePartFinder/Pages/VehiclePartFinderResults.aspx?MAKE=VOLVO&MODEL=850_TURBO&YEAR=1995&CAT=OxygenSensors
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My 94 is a VIN 7 engine and when I shop FCP Groton for the direct fit replacement, they list a Bosch part # 15062.

http://www.fcpgroton.com/product-exec/product_id/5529/nm/1994_1996_Volvo_850_Turbo_Bosch_Direct_Fit_REAR_Oxygen_Sensor/category_id/170
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I have a spare 94 turbo front HO2S in hand.
Can anyone confirm that I can splice the front sensor into the longer wiring harness for the rear sensor and get away with not having to buy a replacement?
If the answer is yes, do the two white wires (preheat) matter which way they are connected?

TIA, Al
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Optimist - half full, Pessimist - half empty, Engineer - The capacity is twice what it needs to be.

I can confirm for you that that front O2 soldered onto the longer rear wires will work fine.

To the best of my knowledge it doesn't matter which way the preheater wires are connected, but I tried to keep mine sorted and connected to their proper mate anyway.

I can't comment on the applicability of the sensor from one year working on another, though my intuition says they're probably very similar if not identical.

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1998 V70 AWD->FWD->AWD Turbo 215k+